Prospective weight change and colon cancer risk in male US health professionals

Role of body mass index and weight change in the risk of cancer: A systematic review and meta-analysis of 66 cohort studies

Background

This study was designed to evaluate the effects of body mass index (BMI) and weight change on the risk of developing cancer overall and cancer at different sites.

Methods

We searched PubMed and other databases up to July 2023 using the keywords related to 'risk', 'cancer', 'weight', 'overweight', and 'obesity'. We identified eligible studies, and the inclusion criteria encompassed cohort studies in English that focused on cancer diagnosis and included BMI or weight change as an exposure factor. Multiple authors performed data extraction and quality assessment, and statistical analyses were carried out using RevMan and R software. We used random- or fixed-effects models to calculate the pooled relative risk (RR) or hazard ratio along with 95% confidence intervals (CIs). We used the Newcastle-Ottawa Scale to assess study quality.

Results

Analysis included 66 cohort studies. Compared to underweight or normal weight, overweight or obesity was associated with an increased risk of endometrial cancer, kidney cancer, and liver cancer but a decreased risk of prostate cancer and lung cancer. Being underweight was associated with an increased risk of gastric cancer and lung cancer but not that of postmenopausal breast cancer or female reproductive cancer. In addition, weight loss of more than five kg was protective against overall cancer risk.

Conclusions

Overweight and obesity increase the risk of most cancers, and weight loss of >5 kg reduces overall cancer risk. These findings provide insights for cancer prevention and help to elucidate the mechanisms underlying cancer development.

Registration

Reviewregistry1786.

Changes in Coffee Intake, Added Sugar and Long-Term Weight Gain - Results from Three Large Prospective US Cohort Studies

BACKGROUND

Consumption of both caffeinated and decaffeinated coffee has been reported to attenuate long-term weight gain. Whether the association between coffee consumption and weight gain depends on the addition of sugar, cream, or coffee whitener remains unclear.

OBJECTIVE

We aimed to study the associations between changes in coffee consumption, caffeine intake, and weight changes by considering the addition of sugar, cream, or a nondairy coffee whitener.

METHODS

We used 3 large prospective cohorts - the Nurses' Health Study (1986 - 2010), Nurses' Health Study II (1991 - 2015) and Health Professional Follow-up Study (1991 - 2014). We applied multivariable linear regression models with robust variance estimators to assess the association of changes in coffee habits within each 4-y interval with concurrent weight changes. Results across the 3 cohorts were pooled using inverse-variance weights.

RESULTS

After multivariable adjustment, each 1 cup per day increment in unsweetened caffeinated coffee was associated with a reduction in 4-y weight gain of -0.12 kg (95 % CI: -0.18, -0.05 kg) and of -0.12 kg (95 % CI: -0.16, -0.08 kg) for unsweetened decaffeinated coffee. The habits of adding cream or nondairy coffee whitener were not significantly linked to weight changes. Adding a teaspoon of sugar was associated with a 4-y weight gain of +0.09 kg (0.07, 0.12 kg). Stratified analyses suggested stronger magnitude of the observed associations with younger age and higher baseline BMI. Neither caffeine nor coffee modified the association of adding sugar to any food or beverage with weight changes.

CONCLUSIONS

An increase in intake of unsweetened caffeinated and decaffeinated coffee was inversely associated with weight gain. The addition of sugar to coffee counteracted coffee's benefit for possible weight management. To the contrary, adding cream or coffee whitener was not associated with greater weight gain.

Motivational interviewing to promote healthy behaviors for obesity prevention in young adults (MOTIVATE): a pilot randomized controlled trial protocol

BACKGROUND

Obesity is a chronic disease and is an established risk factor for other chronic diseases and mortality. Young adulthood is a period when people may be highly amenable to healthy behavior change, develop lifelong healthy behaviors, and when primary prevention of obesity may be feasible. Interventions in early adulthood have the potential for primary or primordial prevention (i.e., preventing risk factors before disease onset). The primary objective of this study is to determine the feasibility of a 6-month behavioral and educational intervention to promote healthy behaviors for obesity prevention among young adults.

METHODS

This is the study protocol for a pilot randomized controlled trial. Young adults (age 18-29) attending McMaster University, Hamilton, Canada, will be recruited and randomized to either the intervention or control. The intervention will include individual motivational interviewing sessions (online or in-person) with a trained interviewer plus educational materials (based on Canada's food guide and physical activity recommendations). The control group will receive educational materials only. The primary feasibility outcomes that will be evaluated as part of this pilot study include enrollment, retention (≥ 80%), data completion (≥ 80% of weights measured, and surveys completed), and participant satisfaction. Secondary clinical outcomes will include body mass index (BMI) change from baseline to 6 months, physical activity, nutrition risk, health-related quality of life mental health, and economic outcomes. Outcomes will be measured remotely using activity trackers, and online questionnaires at baseline and every 2 months. Risk stratification will be applied at baseline to identify participants at high risk of obesity (e.g., due to family or personal history). Exit questionnaires will collect data on how participants felt about the study and cost analysis will be conducted.

DISCUSSION

Our pilot randomized controlled trial will evaluate the feasibility of an obesity prevention intervention in early adulthood and will inform future larger studies for obesity prevention. The results of this study have the potential to directly contribute to the primary prevention of several types of cancer by testing an intervention that could be scalable to public health, post-secondary education, or primary care settings.

TRIAL REGISTRATION

https://clinicaltrials.gov/ct2/show/NCT05264740 . Registered on March 3, 2022.

The risk of colorectal cancer according to obesity status at four-year intervals: a nationwide population-based cohort study

Obesity is a risk factor for colorectal cancer. However, the effect of body weight change on colorectal cancer is uncertain. This study aimed to investigate the relationship between difference in body mass index and the risk of colorectal cancer. In this nationwide population-based cohort study, participants of the national cancer screening program in 2005 and 2009 were enrolled. Difference of body mass index was calculated from screening data from 2005 and 2009. Participants were divided into four groups according to direction of obesity status: non-obese/non-obese, non-obese/obese, obese/non-obese, and obese/obese. The effect of differences in body mass index on colorectal cancer was analyzed. Among 3,858,228 participants, 47,894 (1.24%) participants were newly diagnosed with colorectal cancer during the 9.2 years of follow-up. The incidence of colorectal cancer was higher in the obese/obese group than the non-obese/non-obese group (hazard ratio = 1.08 [1.06-1.11], P trend < 0.001). The men in the obese/obese group had a higher risk of colon cancer than women (hazard ratio = 1.13 [1.10-1.17] in men, and hazard ratio = 1.04 [1.01-1.18] in women, P = 0.001). Persistent obesity was associated with a higher risk of incidence of colorectal cancer.

Exploratory Evaluation of Neopterin and Chitotriosidase as Potential Circulating Biomarkers for Colorectal Cancer

Chronic inflammation is demonstrated to play a direct role in carcinogenesis. Our exploratory study aimed to assess the potential added value of two inflammation biomarkers, chitotriosidase and neopterin, in follow-up evaluation of patients with colorectal cancer (CRC). An observational exploratory study was conducted. Patients with CRC and matched controls (1:1, age, sex, and living environment) were evaluated. The patients with CRC (CRC group) and controls were assessed at baseline (before surgical intervention for patients with CRC). Patients with CRC were also evaluated at 1-year follow-up. Significantly more patients with blood group A (54.5% vs. 25.0%) and smokers (50.0% vs. 22.7%) were in the CRC group. The serum values of chitotriosidase and neopterin were higher in CRC patients than in controls, but only neopterin reached the conventional level of statistical significance (p-value = 0.015). The circulating chitotriosidase and neopterin values decreased significantly at 1-year follow-up (p-value < 0.0001). Patients with higher N- and M-stage showed statistically significant higher levels of chitotriosidase and neopterin at baseline and 1-year follow-up (p-values < 0.03). Circulating chitotriosidase levels also showed statistically significant differences regarding baseline and 1-year follow-up on patients with CRC and different differentiation grades (p-values < 0.02). The circulating levels of neopterin significantly decreased at 1-year follow-up, indicating its potential as a prognostic marker. The circulating values of chitotriosidase and neopterin exhibit significant differences in patients with than without recurrences. Our results support further evaluation of chitotriosidase and neopterin as prognostic markers in patients with CRC.

Assessment of Pre-existing Type 2 Diabetes Mellitus Prevalence and Risk Factors Among Colorectal Cancer Patients in King Abdulaziz Medical City, Jeddah

BACKGROUND

Diabetes mellitus (DM) and cancer are recognized as non-communicable chronic disorders which are among the top ten causes of death globally. In Saudi Arabia, the prevalence of type 2 DM (T2DM) and colorectal cancer (CRC) is alarmingly high. Both T2DM and CRC share common risk factors. In this study, we aim to assess the prevalence of pre-existing T2DM among CRC Saudi patients.

METHODS

In this cross-sectional study, data were collected from the medical records of 275 Saudi adult patients with CRC from 2009 to 2018 at King Abdulaziz Medical City, Jeddah (KAMC-J).

RESULTS

Participants had a mean age of 57.0 years, standard deviation (SD) of 13.0, and were mostly males (60.00%) and Saudi (100.0%). Participants had a mean BMI of 26.42 (7.35) kg/m². The prevalence of pre-existing T2DM in this study was 40.80%. 15.8% of participants were overweight and obese (BMI>30), respectively. The average age of diabetics and non-diabetics was 63.6 (10.64) and 52.73 (12.43), respectively. Diabetic patients are significantly older than non-diabetic patients (p<0.001). The average BMI for diabetics was 26.96 (7.26) kg/m², whereas the average BMI for non-diabetics was 25.93 (7.48) kg/m². No significant differences were found between the two groups.

CONCLUSION

This study provides new insight into the high prevalence of pre-existing T2DM in CRC patients in Saudi Arabia. In particular, the age of diagnosis of CRC in diabetic patients was significantly higher than in non-diabetics.

Female Colon Cancer Metastasis Pattern and Prognosis: A SEER-Based Study

The purpose of this study was to compare the metastatic pattern and prognosis of female colon cancer (FCC) to that of male colon cancer (MCC) to ascertain the independent factors impacting the prognosis of patients with FCC. The data of the present study population were retrieved from the Surveillance, Epidemiology, and End Results (SEER) database. Descriptive analysis, the Kaplan-Meier method, and the Cox regression were used to evaluated FCC characteristics and factors associated with prognosis. There were 56,442 patients diagnosed with FCC, of whom 8,817 had distant metastases. Compared to patients with nonmetastatic FCC, a greater proportion of metastatic FCC patients was less than 60 years of age, black race, and grade III-IV. The primary sites were mainly located on the left side and have more possibility to receive chemotherapy and radiotherapy. Compared to metastatic MCC, a higher proportion of metastatic FCC patients ranged over 60 years of age, black race, treated without chemotherapy, and insurance, while the primary site was located on the right side. Liver and lung were the two most common sites of solitary metastases in CC, and among patients with solitary metastases in CC, patients who had lung metastases had a better prognosis than those who developed other types of metastasizes. Patients with FCC with metastases of the liver had a worse prognosis than their MCC counterparts. Cox multivariate regression analysis showed that the risk ratio was higher in metastatic FCC patients compared to those without metastases. We report the survival comparison of metastatic FCC with nonmetastatic FCC through the SEER database. Our results suggest that it has unique clinicopathological features and differs from metastatic MCC. Furthermore, patients with liver metastatic FCC have a worse prognosis than those with MCC. Emphasis on screening for colon cancer in women and additional clinical care should be paid for, especially for patients with FCC with metastatic liver cancer.

Weight-change trajectory in relation to cancer risk: findings from a nationwide cohort study in South Korea

OBJECTIVE

This study examined relationships between weight-change trajectories and all cancers and obesity-related cancer risks.

METHODS

A total of 1,882,304 men and 899,912 women from the 2002 to 2017 National Health Insurance Service cohort were included. Weight-change trajectories in 2002 to 2009, according to BMI, were determined using group-based trajectory modeling. Cox proportional hazards regression assessed associations between trajectories and cancer incidence.

RESULTS

Overall, >50% of individuals maintained stable weight, as did two-thirds of those in the overweight and obesity groups. A total of 64,725 men and 37,608 women developed incident cancer. Weight stability in overweight or obesity groups was associated with greater cancer risk. In both sexes, higher weight across BMI groups increased risks of all cancers, obesity-related cancers and thyroid, colorectal, stomach, liver, prostate, and postmenopausal breast cancer. Stratified by BMI, weight gain increased risks of all cancers and obesity-related cancers in men with obesity class I and women with overweight. Weight loss decreased risks of obesity-related cancers, thyroid cancer, and kidney cancer among men with overweight, premenopausal breast, endometrial, and ovarian cancer in women with overweight, and obesity-related cancers and thyroid cancer in women with class I obesity.

CONCLUSIONS

Maintaining weight and avoiding weight gain are crucial for reducing cancer risk, but achieving a stable, normal BMI optimizes cancer prevention.

Molecular Biologic and Epidemiologic Insights for Preventability of Colorectal Cancer

The etiology of colorectal cancer (CRC) has been informed from both a molecular biology perspective, which concerns the study of the nature, timing, and consequences of mutations in driver genes, and epidemiology, which focuses on identifying risk factors for cancer. For the most part, these fields have developed independently, and it is thus important to consider them in a more integrated manner. The molecular mutational perspective has stressed the importance of mutations due to replication of adult stem cells, and the molecular fingerprint of most CRCs does not suggest the importance of direct carcinogens. Epidemiology has identified numerous modifiable risk factors that account for most CRCs, most of which are not direct mutagens. The distribution of CRCs across the large bowel is not uniform, which is possibly caused by regional differences in the microbiota. Some risk factors are likely to act through or interact with the microbiota. The mutational perspective informs when risk factors may begin to operate in life and when they may cease to operate. Evidence from the mutational model and epidemiology supports that CRC risk factors begin early in life and may contribute to the risk of early-onset CRC. Later in carcinogenesis, there may be a "point of no return" when sufficient mutations have accumulated, and some risk factors do not affect cancer risk. This period may be at least 5-15 years for some risk factors. A more precise knowledge of timing of risk factor to cancer is required to inform preventive efforts.

Lnc HAGLR Promotes Colon Cancer Progression Through Sponging miR-185-5p and Activating CDK4 and CDK6 in vitro and in vivo

BACKGROUND/AIM

LncRNA plays a key role in tumor progression. HAGLR functions as an oncogene in many cancers. However, the molecular mechanism of HAGLR in colon cancer is still unclear.

METHODS

qRT-PCR was used to measure the expression of HAGLR, miR-185-5p in colon cancer. The expression of CDK4 and CDK6 was detected by Western blot. CCK-8 assay, EdU staining, transwell and Annexin V-FITC/PI assay were used to analyze the effect of HAGLR and miR-185-5p on cell proliferation, invasion, migration and apoptosis. Bioinformatic analysis and luciferase were used to analyze the target genes of HAGLR and miR-185-5p. Nude mice were used to detect mouse tumor changes.

RESULTS

Compared with normal colon cancer tissues and cells, the expression of HAGLR was increased in colon cancer tissues and cells. In addition, the expression of HAGLR down-regulation inhibited the growth, migration, and invasion of colon cancer cells. MiR-185-5p was reduced in colon cancer, and CDK4 and CDK6 acted as target genes of miR-185-5p to regulate the progress of colon cancer. And CDK4 and CDK6 were predicted as downstream targets of miR-185-5p. Finally, it was demonstrated that HAGLR regulated tumor progression in vivo.

CONCLUSION

Lnc HAGLR promoted the development of colon cancer by miR-185-5p/CDK4/CDK6 axis, and lnc HAGLR might be potential target for colon cancer.

Expression of Genes Related to Lipid Handling and the Obesity Paradox in Melanoma: Database Analysis

Background

Publicly available genomic and transcriptomic data in searchable databases allow researchers to investigate specific medical issues in thousands of patients. Many studies have highlighted the role lipids play in cancer initiation and progression and reported nutritional interventions aimed at improving prognosis and survival. Therefore, there is an increasing interest in the role that fat intake may play in cancer. It is known that there is a relationship between BMI and survival in patients with cancer, and that there is an association between a high-fat diet and increased cancer risk. In some cancers, such as colorectal cancer, obesity and high fat intake are known to increase the risk of cancer initiation and progression. On the contrary, in patients undergoing treatment for melanoma, a higher BMI unexpectedly acts as a protective factor rather than a risk factor; this phenomenon is known as the obesity paradox.

Objective

We aimed to identify the molecular mechanism underlying the obesity paradox, with the expectation that this could indicate new effective strategies to reduce risk factors and improve protective approaches.

Methods

In order to determine the genes potentially involved in this process, we investigated the expression values of lipid-related genes in patients with melanoma or colorectal cancer. We used available data from 2990 patients from 3 public databases (IST [In Silico Transcriptomics] Online, GEO [Gene Expression Omnibus], and Oncomine) in an analysis that involved 3 consecutive validation steps. Of this group, data from 1410 individuals were analyzed in the IST Online database (208 patients with melanoma and 147 healthy controls, as well as 991 patients with colorectal cancer and 64 healthy controls). In addition, 45 melanoma, 18 nevi, and 7 healthy skin biopsies were analyzed in another database, GEO, to validate the IST Online data. Finally, using the Oncomine database, 318 patients with melanoma (312 controls) and 435 patients with colorectal cancer (445 controls) were analyzed.

Results

In the first and second database investigated (IST Online and GEO, respectively), patients with melanoma consistently showed significantly (P<.001) lower expression levels of 4 genes compared to healthy controls: CD36, MARCO, FABP4, and FABP7. This strong reduction was not observed in patients with colorectal cancer. An additional analysis was carried out on a DNA-TCGA data set from the Oncomine database, further validating CD36 and FABP4.

Conclusions

The observed lower expression of genes such as CD36 and FABP4 in melanoma may reduce the cellular internalization of fat and therefore make patients with melanoma less sensitive to a high dietary fat intake, explaining in part the obesity paradox observed in patients with melanoma.

Effects of high-fat diet-induced adipokines and cytokines on colorectal cancer development

Colorectal cancer (CRC) is the third most common tumor worldwide, and recent epidemiological studies have indicated that obesity contributes to the morbidity and mortality of CRC. Furthermore, obesity‐related adipokines have been shown to be closely related to the incidence of CRC, but the underlying mechanisms are unclear. Here, we investigated the effects of high‐fat diet‐induced adipokines and cytokines on the development of CRC in vitro and in vivo. For the in vivo assays, we divided 2‐week‐old C57BL/6J‐ApcMin/J male mice into three groups: normal‐fat diet (ND), high‐fat and high‐sugar feed (HFHS), and high‐fat and low‐sugar feed (HFLS). After 1 week, all mice were injected with 20 mg·kg⁻¹ 1,2‐dimethylhydrazine once weekly for 10 consecutive weeks. Body weight, liver weight, epididymal fat weight and blood glucose levels were greatly increased in HFHS and HFLS groups compared with the ND group, and the expression levels of some adipokines and cytokines were obviously higher in HFHS or HFLS mice compared with ND mice. For the in vitro assays, HCT116 CRC cells were treated with sera of ND, HFHS or HFLS groups, or serum‐free media as a negative control. We observed that sera derived from HFHS or HFLS mice that contain excess adipokines and cytokines promoted the proliferation, migration and invasion of HCT116 cells compared with the ND sera‐conditioned medium or serum‐free medium group. Therefore, high‐fat diet‐induced adipokines and cytokines may promote the progression of CRC in vivo and in vitro.

We investigated the effects of high‐fat diet‐induced adipokines and cytokines in the development of colorectal cancer. Some adipokines and cytokines were obviously higher in obese mice than in normal mice. Obesity‐induced adipokines and cytokines promoted the proliferation, migration and invasion of HCT116 cells. Therefore, high‐fat diet‐induced adipokines and cytokines may accelerate the progression of colorectal cancer.

Incremental Elevations in TNFα and IL6 in the Human Colon and Procancerous Changes in the Mucosal Transcriptome Accompany Adiposity

BACKGROUND

Obesity, a risk factor for colorectal cancer, raises systemic levels of proinflammatory mediators. Whether increased levels also reside in the colons of obese individuals and are accompanied by procancerous alterations in the mucosal transcriptome is unknown.

METHODS

Concentrations of TNFα, IL1β, and IL6 in blood and colonic mucosa of 16 lean and 26 obese individuals were examined. Differences in the mucosal transcriptome between the two groups were defined.

RESULTS

Plasma IL6 and TNFα were 1.4- to 3-fold elevated in obese subjects [body mass index (BMI) ≥ 34 kg/m²] compared with the lean controls (P < 0.01). Among individuals with BMI ≥ 34 kg/m² colonic concentrations of IL6 and TNFα were 2- to 3-fold greater than in lean subjects (P < 0.03). In a general linear model, adjusted for NSAID use, colonic IL6 (partial r = 0.41; P < 0.01) and TNFα (partial r = 0.41; P = 0.01) increased incrementally over the entire range of BMIs (18.1-45.7). Regular use of nonsteroidal anti-inflammatory drugs (NSAIDs) was associated with a reduction in colonic IL6 (β = -0.65, P < 0.02). RNA sequencing (NSAID users excluded) identified 182 genes expressed differentially between lean and obese subjects. The two gene networks most strongly linked to changes in expression included several differentially expressed genes known to regulate the procarcinogenic signaling pathways, NFκB and ERK 1/2, in a pattern consistent with upregulation of each in the obese subjects.

CONCLUSIONS

Incremental increases in two major proinflammatory colonic cytokines are associated with increasing BMI, and in the obese state are accompanied by procancerous changes in the transcriptome.

IMPACT

These observations delineate means by which an inflammatory milieu may contribute to obesity-promoted colon cancer.

Height and body fatness and colorectal cancer risk: an update of the WCRF-AICR systematic review of published prospective studies

PURPOSE

There is no published dose-response meta-analysis on the association between height and colorectal cancer risk (CRC) by sex and anatomical sub-site. We conducted a meta-analysis of prospective studies on the association between height and CRC risk with subgroup analysis and updated evidence on the association between body fatness and CRC risk.

METHODS

PubMed and several other databases were searched up to November 2016. A random effects model was used to calculate dose-response summary relative risks (RR's).

RESULTS

47 studies were included in the meta-analyses including 50,936 cases among 7,393,510 participants. The findings support the existing evidence regarding a positive association of height, general and abdominal body fatness and CRC risk. The summary RR were 1.04 [95% (CI)1.02-1.05, I² = 91%] per 5 cm increase in height, 1.02 [95% (CI)1.01-1.02, I² = 0%] per 5 kg increase in weight, 1.06 [95% (CI)1.04-1.07, I² = 83%] per 5 kg/m2 increase in BMI, 1.02 [95% (CI)1.02-1.03, I² = 4%] per 10 cm increase in waist circumference, 1.03 [95% (CI)1.01-1.05, I² = 16%] per 0.1 unit increase in waist to hip ratio. The significant association for height and CRC risk was similar in men and women. The significant association for BMI and CRC risk was stronger in men than in women.

CONCLUSION

The positive association between height and risk of CRC suggests that life factors during childhood and early adulthood might play a role in CRC aetiology. Higher general and abdominal body fatness during adulthood are risk factors of CRC and these associations are stronger in men than in women.

The Future Colorectal Cancer Burden Attributable to Modifiable Behaviors: A Pooled Cohort Study

BACKGROUND

Previous estimates of the colorectal cancer (CRC) burden attributed to behaviors have not considered joint effects, competing risk, or population subgroup differences.

METHODS

We pooled data from seven prospective Australian cohort studies (n = 367 058) and linked them to national registries to identify CRCs and deaths. We estimated the strength of the associations between behaviors and CRC risk using a parametric piecewise constant hazards model, adjusting for age, sex, study, and other behaviors. Exposure prevalence was estimated from contemporary National Health Surveys. We calculated population attributable fractions for CRC preventable by changes to current behaviors, accounting for competing risk of death and risk factor interdependence. Statistical tests were two-sided.

RESULTS

During the first 10 years of follow-up, there were 3471 incident CRCs. Overweight or obesity explained 11.1%, ever smoking explained 10.7% (current smoking 3.9%), and drinking more than two compared with two or fewer alcoholic drinks per day explained 5.8% of the CRC burden. Jointly, these factors were responsible for 24.9% (95% confidence interval [CI] = 19.7% to 29.9%) of the burden, higher for men (36.7%) than women (13.2%, P difference < .001). The burden attributed to these factors was also higher for those born in Australia (28.7%) than elsewhere (16.8%, P difference = .047). We observed modification of the smoking-attributable burden by alcohol consumption and educational attainment, and modification of the obesity-attributable burden by age group and birthplace.

CONCLUSIONS

We produced up-to-date estimates of the future CRC burden attributed to modifiable behaviors. We revealed novel differences between men and women, and other high-CRC burden subgroups that could potentially benefit most from programs that support behavioral change and early detection.

The role of the lipidome in obesity-mediated colon cancer risk

Obesity is a state of chronic inflammation influenced by lipids such as fatty acids and their secondary oxygenated metabolites deemed oxylipids. Many such lipid mediators serve as potent signaling molecules of inflammation, which can further alter lipid metabolism and lead to carcinogenesis. For example, sphingosine-1-phosphate activates cyclooxygenase-2 in endothelial cells resulting in the conversion of arachidonic acid (AA) to prostaglandin E₂ (PGE₂). PGE₂ promotes colon cancer cell growth. In contrast, the less studied path of AA oxygenation via cytochrome p450 enzymes produces epoxyeicosatetraenoic acids (EETs), whose anti-inflammatory properties cause shrinking of enlarged adipocytes, a characteristic of obesity, through the liberation of fatty acids. It is now thought that EET depletion occurs in obesity and may contribute to colon cell carcinogenesis. Meanwhile, gangliosides, a type of sphingolipid, are cell surface signaling molecules that contribute to the apoptosis of colon tumor cells. Many of these discoveries have been made recently and the mechanisms are still not fully understood, leading to an exciting new chapter of lipidomic research. In this review, mechanisms behind obesity-associated colon cancer are discussed with a focus on the role of small lipid signaling molecules in the process. Specifically, changes in lipid metabolite levels during obesity and the development of colon cancer, as well as novel biomarkers and targets for therapy, are discussed.

Changes in Adult BMI and Waist Circumference Are Associated with Increased Risk of Advanced Colorectal Neoplasia

BACKGROUND

Waist circumference (WC) is a stronger predictor of colon cancer (CRC) risk than body mass index (BMI). However, how well change in either WC or BMI predicts risk of advanced colorectal neoplasia (AN) is unclear.

AIMS

To determine the relationship between change in BMI and WC from early adulthood to later age and the risk of AN and which change measure is a stronger predictor.

METHODS

In 4500 adults, ages 50-80, with no previous neoplasia and undergoing screening colonoscopy, BMI and WC at age 21 and at time of screening were reported. Changes in BMI and WC were defined using universal risk cutoffs. Known CRC risk factors were controlled in the logistic models.

RESULTS

Overall, model statistics showed WC change (omnibus test χ ² = 10.15, 2 DF, p value = 0.006) was a statistically stronger predictor of AN than BMI change (omnibus test χ ² = 5.66, 5 DF, p value = 0.34). Independent of BMI change, participants who increased WC (OR 1.44; 95% CI 1.05-1.96) or maintained a high-risk WC (OR 2.50; 95% CI 1.38-4.53) at age 21 and at screening had an increased risk of AN compared to those with a low-risk WC. Study participants who were obese at age 21 and at screening had an increased risk of AN (OR 1.87; 95% CI 1.08-3.23) compared to those who maintained a healthy BMI. Maintaining an overweight BMI or increasing BMI was not associated with AN.

CONCLUSIONS

Maintaining an unhealthy BMI and WC throughout adult life may increase risk of AN. WC change may be a better predictor of AN than BMI change.

Effect of Weight Gain and Weight Loss on In Vivo Colonocyte Proliferation Rate in People with Obesity

OBJECTIVE

To evaluate the effects of diet-induced changes in energy balance and body weight on in vivo colonocyte fractional proliferation rates (FPR) in people with obesity.

METHODS

In vivo colonocyte FPR was assessed in 31 men and women with obesity (BMI: 35.4 ± 4.0 kg/m2 , age: 52.6 ± 8.9 years) before and after diet-induced weight loss, weight gain, or weight maintenance. Subjects ingested aliquots of 2 H2 O (heavy water) daily for 4 to 7 days, followed by flexible sigmoidoscopy with colon biopsies to assess the incorporation of 2 H into the DNA of dividing colonocytes.

RESULTS

Colonocyte FPR averaged 12.7% ± 3.8% per day and correlated directly with intra-abdominal adipose tissue (IAAT) volume (r = 0.364, P = 0.044). Colonocyte FPR decreased in the weight loss group, did not change in the weight maintenance group, and increased in the weight gain group. The change in colonocyte FPR correlated directly with the percent change in body weight (r = 0.409, P = 0.028) and IAAT volume (r = 0.598, P = 0.001).

CONCLUSIONS

A high-calorie diet and weight gain increase, whereas a low-calorie diet and weight loss decrease, in vivo colonocyte proliferation rate in people with obesity. These results suggest that changes in energy balance influence the risk of developing colon cancer in people with obesity by regulating colonic mucosal growth rates.

Adiponectin and Intelectin-1: Important Adipokine Players in Obesity-Related Colorectal Carcinogenesis

Overweight is believed to be associated with colorectal cancer risk. Adipose tissue is loose connective tissue composed of adipocytes. It is now recognized as a major endocrine organ, secreting humoral factors collectively called adipokines. Aberrant hormonal systems consisting of modulated adipokines and their receptors are thought to play a role in colorectal carcinogenesis and cancer progression in obese conditions. However, it is still unclear whether and how each adipokine relates to colorectal carcinogenesis. Notably, a couple of molecules that were initially proposed to be obesity-related adipokines were disqualified by subsequent studies. The adipokines, adiponectin, and intelectin-1 (also known as omentin-1), whose levels are decreased in obesity, act as tumor suppressor factors in various cancers. Numerous studies have demonstrated a link between the insufficient expression and function of adiponectin and its receptor, T-cadherin, in colorectal carcinogenesis. Moreover, our recent study indicated that loss of TMEM207, which is critical for the proper processing of intelectin-1 in the colon mucosa, leads to insufficient intelectin-1 production, thus participating in colorectal carcinogenesis. Here, we discuss the recent understanding of the role of adipokines in colorectal carcinogenesis and subsequently describe the potent tumor suppressor roles of intelectin-1 and TMEM207 in colorectal cancer.

Adiponectin and Intelectin-1: Important Adipokine Players in Obesity-Related Colorectal Carcinogenesis

Overweight is believed to be associated with colorectal cancer risk. Adipose tissue is loose connective tissue composed of adipocytes. It is now recognized as a major endocrine organ, secreting humoral factors collectively called adipokines. Aberrant hormonal systems consisting of modulated adipokines and their receptors are thought to play a role in colorectal carcinogenesis and cancer progression in obese conditions. However, it is still unclear whether and how each adipokine relates to colorectal carcinogenesis. Notably, a couple of molecules that were initially proposed to be obesity-related adipokines were disqualified by subsequent studies. The adipokines, adiponectin, and intelectin-1 (also known as omentin-1), whose levels are decreased in obesity, act as tumor suppressor factors in various cancers. Numerous studies have demonstrated a link between the insufficient expression and function of adiponectin and its receptor, T-cadherin, in colorectal carcinogenesis. Moreover, our recent study indicated that loss of TMEM207, which is critical for the proper processing of intelectin-1 in the colon mucosa, leads to insufficient intelectin-1 production, thus participating in colorectal carcinogenesis. Here, we discuss the recent understanding of the role of adipokines in colorectal carcinogenesis and subsequently describe the potent tumor suppressor roles of intelectin-1 and TMEM207 in colorectal cancer.

Diet-induced weight loss leads to a switch in gene regulatory network control in the rectal mucosa

BACKGROUND

Weight loss may decrease risk of colorectal cancer in obese individuals, yet its effect in the colorectum is not well understood. We used integrative network modeling, Passing Attributes between Networks for Data Assimilation, to estimate transcriptional regulatory network models from mRNA expression levels from rectal mucosa biopsies measured pre- and post-weight loss in 10 obese, pre-menopausal women.

RESULTS

We identified significantly greater regulatory targeting of glucose transport pathways in the post-weight loss regulatory network, including "regulation of glucose transport" (FDR=0.02), "hexose transport" (FDR=0.06), "glucose transport" (FDR=0.06) and "monosaccharide transport" (FDR=0.08). These findings were not evident by gene expression analysis alone. Network analysis also suggested a regulatory switch from NFΚB1 to MAX control of MYC post-weight loss.

CONCLUSIONS

These network-based results expand upon standard gene expression analysis by providing evidence for a potential mechanistic alteration caused by weight loss.

Is obesity an advantage in patients with colorectal cancer?

Obesity/higher BMI appears to be important determinants in the development of colon cancer as well as in predicting outcomes in the adjuvant setting in these patients. These associations seem to be stronger for men and tend to be 'J-shaped', with worse outcomes in both lower and upper BMI categories than in the middle categories. How this factors in the metastatic setting is less clear. A recent pooled analysis of patients with metastatic colorectal cancer receiving bevacizumab in the first-line setting observed that patients with the lowest BMI had the lowest median overall survival. An incremental BMI increase of 5 kg/m(2) led to actually a decrease in the risk of death (hazard ratio, 0.911 [95% CI, 0.879-0.944]). The observed association does not necessarily mean that obesity is an advantage for patients with metastatic colorectal cancer. More likely, it is conceivable that, in patients with metastatic colorectal cancer with a lower BMI, the effects of cancer-related cachexia may be more deleterious than the potential adverse events related to a higher BMI. In patients already diagnosed with metastatic disease, studying how body weight affects tumor biology and treatment-related decisions are important considerations.

Body weight, fat distribution and colorectal cancer risk: a report from cohort studies of 134255 Chinese men and women

OBJECTIVE

To evaluate the association of body size and fat distribution with risk of colorectal cancer (CRC) in Chinese men and women.

DESIGN

Population-based, prospective cohort study.

SUBJECTS

The analysis included 134 255 Chinese adults enrolled in the Shanghai Women’s Health Study and the Shanghai Men’s Health Study, with an average follow-up of 11.0 and 5.5 years, respectively.

MEASUREMENTS

Waist circumference (WC), body mass index (BMI) and waist-to-hip ratio (WHR) were measured by trained interviewers at baseline. Multivariable Cox models were used to calculate adjusted hazard ratios (HRs) for incident CRC.

RESULTS

A total of 935 incident CRC cases were identified. Both measures of general adiposity (measured by BMI) and central adiposity (measured by WHR and WC) were significantly associated with increased risk of colon cancer in men but not in women. Multivariable adjusted HRs for colon cancer in men in the highest compared with the lowest quintiles were 2.15 (95% CI: 1.35-3.43; P for trend = 0.0006) for BMI, 1.97 (95% CI: 1.19-3.24; P for trend = 0.0004) for WHR and 2.00 (95% CI: 1.21-3.29; P for trend = 0.0002) for WC. The BMI-associated risk was attenuated in analyses stratified by WHR, while the WHR-associated risk remained significant in the high BMI stratum (HR for comparison of extreme tertiles of WHR: 3.38, 95% CI: 1.47-7.75; P for trend =0.0002). None of these anthropometric measures were significantly associated with rectal cancer.

CONCLUSION

Obesity, particularly central obesity, was associated with increased risk of colon cancer in men.

Body weight gain and risk of colorectal cancer: a systematic review and meta-analysis of observational studies

While the relationship between body mass index as an indicator of excess body weight and the risk of colorectal cancer (CRC) is well established, the association between body weight gain in adulthood and risk of CRC remains unresolved. We quantified this association in a meta-analysis of 12 observational studies published until November 2014 with a total of 16,151 incident CRC cases. Random effect models were used to obtain summary relative risks (RR) and 95% confidence intervals (95% CIs). Between-study heterogeneity was assessed using I(2) statistics. Overall, the summary RR (95% CI) was 1.22 (1.14-1.30) for high body weight gain (midpoint: 15.2 kg) compared with stable weight (P for heterogeneity = 0.182; I(2) = 21.2%). In a dose-response analysis, each 5 kg weight gain was associated with a 4% (95% CI: 2%-5%) higher risk of CRC. The association persisted after adjustment for body weight at younger age and was present for both men and women, as well as for colon and rectal cancer. Differences by sex were detected for colon cancer (P for interaction = 0.003, with higher risk for men than women), but not for rectal cancer (P for interaction = 0.613). In conclusion, these data underscore the importance of body weight management from early adulthood onwards for the prevention of CRC development.

Obesity as a risk factor in cancer: A national consensus of the Spanish Society for the Study of Obesity and the Spanish Society of Medical Oncology

In the last few years, many prospective studies have demonstrated a clear association between obesity and cancers of the colon and rectum, breast in post-menopausal women, endometrium, kidney, oesophagus and pancreas. Obesity is also associated with a high risk of recurrence and cancer-related death. The pathophysiology of obesity involves various changes that may be implicated in the relationship between obesity and cancer, such as excess inflammatory cytokines and chronic inflammation, hyperinsulinaemia, insulin resistance, and raised leptin and oestrogens. The Spanish Society for the Study of Obesity and the Spanish Society of Medical Oncology have signed a cooperation agreement to work together towards reducing the impact of obesity in cancer. Preventing obesity prevents cancer.

Weight change and risk of colorectal cancer: a systematic review and meta-analysis

Results from cohort studies of adult weight gain and risk of colorectal cancer are inconsistent. We conducted a systematic review and meta-analysis of prospective studies assessing the association of change in weight/body mass index with colorectal cancer risk. We searched Scopus and Web of Science up to June 2014 and supplemented the search with manual searches of the reference lists of the identified articles. Thirteen studies published between 1997 and 2014 were pooled by using a random-effects model, and potential heterogeneity was explored by fitting meta-regression models. The highest weight gain category, measured by weight/body mass index, compared with a reference category, was associated with increased risk of colorectal cancer (hazard ratio (HR) = 1.16, 95% confidence interval (CI): 1.08, 1.24), whereas no association was found for weight loss (HR = 0.96, 95% CI: 0.89, 1.05). There was no suggestion of heterogeneity across studies. For dose response, a 5-kg weight gain was associated with a slightly increased risk of colorectal cancer (HR = 1.03, 95% CI: 1.02, 1.05), with some heterogeneity observed (I(2) = 42%; P = 0.02), which was partially explained by sex (ratio of HRs = 1.03, 95% CI: 1.00, 1.07). In this meta-analysis, gain in weight/body mass index was positively associated with colorectal cancer risk.

Adulthood Weight Change and Risk of Colorectal Cancer in the Nurses' Health Study and Health Professionals Follow-up Study

We investigated the association between adulthood weight change and colorectal cancer risk in a prospective study with 24 to 34 years of follow-up among 90,988 women and 46,679 men. The primary exposures included weight change from early adulthood (age = 18 years for women, 21 years for men) to baseline enrollment (median age = 43 years for women, 52 years for men), and from baseline to present. In the secondary analyses, we also assessed 4-year weight change during follow-up, and during premenopausal (from age 18 years to menopause) and postmenopausal (from menopause to present) periods in women. Compared to men maintaining their weight from age 21 to baseline, those who gained 20 kg or more were at a higher risk of colorectal cancer (relative risk [RR], 1.64; 95% confidence interval [CI], 1.15-2.35, Ptrend < 0.001), whereas those who lost 8 kg or more had a lower risk (RR, 0.61; 95% CI, 0.30-1.22, Ptrend = 0.003). Similar but weaker associations were found in women and the corresponding RRs were 1.38 (95% CI, 1.13-1.69, Ptrend < 0.001) and 0.80 (95% CI, 0.58-1.09, Ptrend = 0.21). Weight change from baseline to present was not associated with colorectal cancer risk. Four-year weight change during follow-up was positively associated with colorectal cancer risk in men (Ptrend = 0.03) but not in women (Ptrend = 0.42). In addition, in women, weight change before, but not after, menopause was associated with colorectal cancer risk. Our findings provide further scientific rationale for recommendations to maintain a healthy body weight during adulthood. A potential differential association according to sex and timing of weight change warrants further investigation.

Adult weight gain and adiposity-related cancers: a dose-response meta-analysis of prospective observational studies

BACKGROUND

Adiposity, measured by body mass index, is implicated in carcinogenesis. While adult weight gain has diverse advantages over body mass index in measuring adiposity, systematic reviews on adult weight gain in relation to adiposity-related cancers are lacking.

METHODS

PubMed and Embase were searched through September 2014 for prospective observational studies investigating the relationship between adult weight gain and the risk of 10 adiposity-related cancers. Dose-response meta-analyses were performed using a random-effects model to estimate summary relative risk (RR) and 95% confidence interval (CI) for each cancer type. All statistical tests were two-sided.

RESULTS

A total of 50 studies were included. For each 5 kg increase in adult weight gain, the summary relative risk was 1.11 (95% CI = 1.08 to 1.13) for postmenopausal breast cancer among no- or low-hormone replacement therapy (HRT) users, 1.39 (95% CI = 1.29 to 1.49) and 1.09 (95% CI = 1.02 to 1.16) for postmenopausal endometrial cancer among HRT nonusers and users, respectively, 1.13 (95% CI = 1.03 to 1.23) for postmenopausal ovarian cancer among no or low HRT users, 1.09 (95% CI = 1.04 to 1.13) for colon cancer in men. The relative risk of kidney cancer comparing highest and lowest level of adult weight gain was 1.42 (95% CI = 1.11 to 1.81). Adult weight gain was unrelated to cancers of the breast (premenopausal women, postmenopausal HRT users), prostate, colon (women), pancreas, and thyroid. An increase in risk associated with adult weight gain for breast cancer was statistically significantly greater among postmenopausal women (P(heterogeneity) = .001) and HRT nonusers (P(heterogeneity) = .001); that for endometrial cancer was alike among HRT nonusers (P(heterogeneity) = .04).

CONCLUSIONS

Avoiding adult weight gain itself may confer protection against certain types of cancers, particularly among HRT nonusers.

Body mass index and risk of second obesity-associated cancers after colorectal cancer: a pooled analysis of prospective cohort studies

PURPOSE

To determine whether prediagnostic body mass index (BMI) is associated with risk of second obesity-associated cancers in colorectal cancer (CRC) survivors, and whether CRC survivors have increased susceptibility to obesity-associated cancer compared with cancer-free individuals.

PATIENTS AND METHODS

Incident first primary CRC cases (N = 11,598) were identified from five prospective cohort studies. We used Cox proportional hazards regression models to examine associations between baseline (prediagnostic) BMI and risk of second obesity-associated cancers (postmenopausal breast, kidney, pancreas, esophageal adenocarcinoma, endometrium) in CRC survivors, and compared associations to those for first obesity-associated cancers in the full cohort.

RESULTS

Compared with survivors with normal prediagnostic BMI (18.5-24.9 kg/m(2)), those who were overweight (25-29.9 kg/m(2)) or obese (30+ kg/m(2)) had greater risk of a second obesity-associated cancer (n = 224; overweight hazard ratio [HR], 1.39; 95% CI, 1.01 to 1.92; obese HR, 1.47; 95% CI, 1.02 to 2.12; per 5-unit change in BMI HR, 1.12; 95% CI, 0.98 to 1.29). The magnitude of risk for developing a first primary obesity-associated cancer was similar (overweight HR, 1.18; 95% CI, 1.14 to 1.21; obese HR, 1.61; 95% CI, 1.56 to 1.66; per 5-unit change in BMI HR, 1.23; 95% CI, 1.21 to 1.24). Before diagnosis CRC patients were somewhat more likely than the overall cohort to be overweight (44% v 41%) or obese (25% v 21%).

CONCLUSION

CRC survivors who were overweight or obese before diagnosis had increased risk of second obesity-associated cancers compared with survivors with normal weight. The risks were similar in magnitude to those observed for first cancers in this population, suggesting increased prevalence of overweight or obesity, rather than increased susceptibility, may contribute to elevated second cancer risks in colorectal cancer survivors compared with the general population. These results support emphasis of existing weight guidelines for this high-risk group.

Overweight, obesity and endometrial cancer risk: results from a systematic review and meta-analysis

AIM

Findings from recent studies suggest that obesity may be associated with an increased risk of endometrial cancer, but several earlier studies were less conclusive. Here we strive to estimate this relationship in a meta-analysis of published data.

METHODS

We searched Pubmed and Embase for studies on body mass index and the risk of endometrial cancer, published from 1989 to 2011. Data were independently extracted and analyzed using random or fixed effects meta-analysis depending on the degree of heterogeneity.

RESULTS

Seven cohort studies and 11 case-control studies were included in the meta-analysis. Overall, the conditions of excess body weight ([EBW] defined as body mass index [BMI] ≥25 kg/m²), obesity (BMI ≥30 kg/m²) and overweight (25< BMI <30 kg/m²) were associated with an increased risk of endometrial cancer (relative risk [RR] for EBW=1.62, 95% confidence interval [CI], 1.39-1.89; for obesity RR=2.54, 95% CI, 2.11-3.06; for overweight RR=1.32, 95% CI, 1.16-1.50). Subgroup analyses showed that the positive associations were independent of study design, geographic locations, self-reported BMI, alcohol use, smoking habit, history of diabetes, hormone therapy, age at menarche, age at menopause, parity, and age at first full term pregnancy. However, there was no statistically significant association between EBW and endometrial cancer risk for measured BMI (for EBW RR=1.29, 95% CI, 0.66-2.53).

CONCLUSIONS

The findings from this meta-analysis strongly support that the conditions of EBW, overweight, and obesity are all associated with an increased risk of endometrial cancer. Also, the strength of the association increases with increasing BMI.

Mechanisms linking excess adiposity and carcinogenesis promotion

Obesity constitutes one of the most important metabolic diseases being associated to insulin resistance development and increased cardiovascular risk. Association between obesity and cancer has also been well established for several tumor types, such as breast cancer in post-menopausal women, colorectal, and prostate cancer. Cancer is the first death cause in developed countries and the second one in developing countries, with high incidence rates around the world. Furthermore, it has been estimated that 15-20% of all cancer deaths may be attributable to obesity. Tumor growth is regulated by interactions between tumor cells and their tissue microenvironment. In this sense, obesity may lead to cancer development through dysfunctional adipose tissue and altered signaling pathways. In this review, three main pathways relating obesity and cancer development are examined: (i) inflammatory changes leading to macrophage polarization and altered adipokine profile; (ii) insulin resistance development; and (iii) adipose tissue hypoxia. Since obesity and cancer present a high prevalence, the association between these conditions is of great public health significance and studies showing mechanisms by which obesity lead to cancer development and progression are needed to improve prevention and management of these diseases.

Weight change later in life and colon and rectal cancer risk in participants in the EPIC-PANACEA study

BACKGROUND

A moderate association exists between body mass index (BMI) and colorectal cancer. Less is known about the effect of weight change.

OBJECTIVE

We investigated the relation between BMI and weight change and subsequent colon and rectal cancer risk.

DESIGN

This was studied among 328,781 participants in the prospective European Prospective Investigation into Cancer-Physical Activity, Nutrition, Alcohol, Cessation of Smoking, Eating study (mean age: 50 y). Body weight was assessed at recruitment and on average 5 y later. Self-reported weight change (kg/y) was categorized in sex-specific quintiles, with quintiles 2 and 3 combined as the reference category (men: -0.6 to 0.3 kg/y; women: -0.4 to 0.4 kg/y). In the subsequent years, participants were followed for the occurrence of colon and rectal cancer (median period: 6.8 y). Multivariable Cox proportional hazards regression analyses were used to study the association.

RESULTS

A total of 1261 incident colon cancer and 747 rectal cancer cases were identified. BMI at recruitment was statistically significantly associated with colon cancer risk in men (HR: 1.04; 95% CI: 1.02, 1.07). Moderate weight gain (quintile 4) in men increased risk further (HR: 1.32; 95% CI: 1.04, 1.68), but this relation did not show a clear trend. In women, BMI or weight gain was not related to subsequent risk of colon cancer. No statistically significant associations for weight loss and colon cancer or for BMI and weight changes and rectal cancer were found.

CONCLUSIONS

BMI attained at adulthood was associated with colon cancer risk. Subsequent weight gain or loss was not related to colon or rectal cancer risk in men or women.

Slowing down of adult body mass index trend increases in England: a latent class analysis of cross-sectional surveys (1992-2010)

BACKGROUND

The prevalence of excess body weight, commonly measured as body mass index (BMI)≥25 kg m(-2), has increased substantially in many populations worldwide over the past three decades, but the rate of increase has slowed down in some western populations.

OBJECTIVE

We address the hypothesis that the slowing down of BMI trend increases in England reflects a majority sub-population resistant to further BMI elevation.

DESIGN

Pseudo-panel data derived from annual cross-sectional surveys, the Health Surveys for England (1992-2010). Trends in median BMI values were explored using regression models with splines, and gender-specific mixture model (latent class analysis) were fit to take an account of increasing BMI distribution variance with time and identify hidden subgroups within the population.

SUBJECTS

BMI was available for 164 155 adults (men: 76 382; women: 87 773).

RESULTS

Until 2001, the age-adjusted yearly increases in median BMI were 0.140 and 0.139 kg m(-2) for men and women, respectively, decreasing thereafter to 0.073 and 0.055 kg m(-2) (differences between time periods, both P-values<0.0001). The mixture model identified two components--a normal BMI and a high BMI sub-population--the proportions for the latter were 23.5% in men and 33.7% in women. The remaining normal BMI populations were 'resistant' with minimal increases in mean BMI values over time. By age, mean BMI values in the normal BMI sub-population increased greatest between 20 and 34 years for men; for women, the increases were similar throughout age groups (slope differences, P<0.0001).

CONCLUSION

In England, recent slowing down of adult BMI trend increases can be explained by two sub-populations--a high BMI sub-population getting 'fatter' and a majority 'resistant' normal BMI sub-population. These findings support a targeted, rather than a population-wide, policy to tackle the determinants of obesity.

The impact of missing data on analyses of a time-dependent exposure in a longitudinal cohort: a simulation study

BACKGROUND

Missing data often cause problems in longitudinal cohort studies with repeated follow-up waves. Research in this area has focussed on analyses with missing data in repeated measures of the outcome, from which participants with missing exposure data are typically excluded. We performed a simulation study to compare complete-case analysis with Multiple imputation (MI) for dealing with missing data in an analysis of the association of waist circumference, measured at two waves, and the risk of colorectal cancer (a completely observed outcome).

METHODS

We generated 1,000 datasets of 41,476 individuals with values of waist circumference at waves 1 and 2 and times to the events of colorectal cancer and death to resemble the distributions of the data from the Melbourne Collaborative Cohort Study. Three proportions of missing data (15, 30 and 50%) were imposed on waist circumference at wave 2 using three missing data mechanisms: Missing Completely at Random (MCAR), and a realistic and a more extreme covariate-dependent Missing at Random (MAR) scenarios. We assessed the impact of missing data on two epidemiological analyses: 1) the association between change in waist circumference between waves 1 and 2 and the risk of colorectal cancer, adjusted for waist circumference at wave 1; and 2) the association between waist circumference at wave 2 and the risk of colorectal cancer, not adjusted for waist circumference at wave 1.

RESULTS

We observed very little bias for complete-case analysis or MI under all missing data scenarios, and the resulting coverage of interval estimates was near the nominal 95% level. MI showed gains in precision when waist circumference was included as a strong auxiliary variable in the imputation model.

CONCLUSIONS

This simulation study, based on data from a longitudinal cohort study, demonstrates that there is little gain in performing MI compared to a complete-case analysis in the presence of up to 50% missing data for the exposure of interest when the data are MCAR, or missing dependent on covariates. MI will result in some gain in precision if a strong auxiliary variable that is not in the analysis model is included in the imputation model.

Adult weight change and risk of colorectal cancer in the European Prospective Investigation into Cancer and Nutrition

AIM

Weight change during adult life may reflect metabolic changes and influence colorectal cancer (CRC) development, but such role is not well established. We aimed to explore the association between adult weight change (from age 20 to 50) and CRC risk. In particular, we investigated differences according to colon and rectal cancer, sex and measures of attained adiposity.

METHODS

We included 201,696 participants from six participating countries in the European Prospective Investigation into Cancer and Nutrition (1992-2010). During a mean follow-up of 11.2 years 2384 (1194 in men and 1190 in women) incident CRC cases occurred. Cox proportional hazard models adjusted for body mass index at age 20 and lifestyle factors at study recruitment were used to calculate hazard ratios (HRs) and 95% confidence intervals (CIs).

RESULTS

After multivariable adjustment, each kg of weight gained annually from age 20 to 50 was associated with a 60% higher risk of colon cancer (95% CI 1.20-2.09), but not rectal cancer (HR 1.13, 95% CI 0.79-1.62, P(interaction)=0.04). The higher risk of colon cancer was restricted to people with high attained waist circumference at age 50 (HR 1.82, 95%CI 1.14-2.91, P(interaction)=0.02). Results were not different in men and women (P(interaction)=0.81).

CONCLUSION(S)

Adult weight gain, as reflected by attained abdominal obesity at age 50, increases colon cancer risk in both men and women. These data underline the importance of weight management and metabolic health maintenance in early adult life years for colon cancer prevention.

Obesity and risk of colorectal cancer: a systematic review of prospective studies

Background

Mounting evidence indicates that obesity may be associated with the risk of colorectal cancer (CRC). To conduct a systematic review of prospective studies assessing the association of obesity with the risk of CRC using meta-analysis.

Methodology/Principal Findings

Relevant studies were identified by a search of MEDLINE and EMBASE databases before January 2012, with no restrictions. We also reviewed reference lists from retrieved articles. We included prospective studies that reported relative risk (RR) estimates with 95% confidence intervals (CIs) for the association between general obesity [measured using body mass index (BMI)] or central obesity [measured using waist circumference (WC)] and the risk of colorectal, colon, or rectal cancer. Approximately 9, 000, 000 participants from several countries were included in this analysis. 41 studies on general obesity and 13 studies on central obesity were included in the meta-analysis. The pooled RRs of CRC for the obese vs. normal category of BMI were 1.334 (95% CI, 1.253–1.420), and the highest vs. lowest category of WC were 1.455 (95% CI, 1.327–1.596). There was heterogeneity among studies of BMI (P<0.001) but not among studies of WC (P = 0.323).

Conclusions

Both of general and central obesity were positively associated with the risk of CRC in this meta-analysis.

Body mass index at different adult ages, weight change, and colorectal cancer risk in the National Institutes of Health-AARP Cohort

The authors investigated the relations of body mass index at different ages and adult weight change to incident colorectal cancer risk in the prospective National Institutes of Health-AARP Diet and Health Study (1995-1996), using a subcohort with repeated recall weights (273,679 participants; mean baseline age = 62.8 years). During 2,509,662 person-years follow-up, 4076 incident colorectal cancers were ascertained. For men, an increased risk of colon cancer but not rectal cancer was associated with body mass index at baseline age (per 5-kg/m(2) increase, hazard ratio (HR) = 1.18, 95% confidence interval (CI): 1.11, 1.25), at age 50 years (HR = 1.18, 95% CI: 1.10, 1.26), and at age 35 years (HR = 1.16, 95% CI: 1.07, 1.25) but less so at age 18 years. Weight gained between the ages of 18 and 35 years and between 18 years of age and the baseline age was associated with an increased risk of colon cancer in men (per 0.5-kg/year increase, HR = 1.18, 95% CI: 1.11, 1.25 and HR = 1.29, 95% CI: 1.16, 1.56, respectively). For women, relations throughout were weaker than those observed for men. These findings suggest that weight gains during early to middle adulthood have important influences on colon cancer risk, especially in men.

Obesity and colorectal cancer

Obesity is a risk factor for colorectal cancer based on its molecular and metabolic effects on insulin and IGF-1, leptin, adipocytokines, and sex hormones. Obese men have a higher risk of colorectal cancer compared with normal weight men, but the association between obesity and rectal cancer is weaker than with colon cancer. There is a weaker association between obesity and colon cancer in women than in men, and no appreciable association between obesity and rectal cancer in women. Although obesity does not seem to have an effect on the number of lymph nodes harvested with resection, obesity does seem to be associated with more-aggressive colorectal cancers in a handful of studies. Survival and local recurrence studies are contradictory with no conclusive evidence that obesity predisposes to worse overall survival or increased recurrence in colon and rectal cancers. The literature is not definitive as far as overall morbidity and mortality rates in the obese are concerned, though obese rectal cancer patients seem to incur proportionally more morbidity and mortality. Preexisting steatosis or steatohepatitis in obese colorectal cancer patients or chemotherapy-induced liver dysfunction may lead to an increased mortality in obese patients with colorectal liver metastases. Diabetes may cause poorer response to neoadjuvant therapy in rectal cancer and contribute to higher mortality and recurrence in colon cancer.

A systematic review of the impact of weight loss on cancer incidence and mortality

Obesity is well recognized as a significant risk factor for certain cancers; however, a corresponding risk reduction with weight loss is not yet clearly defined. This review aims to examine the literature investigating the effect of all types of weight loss on cancer incidence and mortality, and to more clearly describe the relationship between these two factors. A literature search identified 34 publications reporting weight loss data in relation to cancer incidence or mortality. All except one were observational studies and the majority used self-reported weights and did not define intentionality of weight loss. 16/34 studies found a significant inverse association between weight loss and cancer incidence or mortality. The remainder returned null findings. The observed association was more consistently seen in studies that investigated the effect of intentional weight loss (5/6 studies) and the risk reduction was greatest for obesity-related cancers and in women. In conclusion, intentional weight loss does result in a decreased incidence of cancer, particularly female obesity-related cancers. However, there is a need for further evaluation of sustained intentional weight loss in the obese with less reliance on self-reported weight data and more focus on male populations.

The maternal womb: a novel target for cancer prevention in the era of the obesity pandemic?

The dramatic rise in worldwide prevalence of obesity has necessitated the search for more efficacious antiobesity strategies to counter the increased cancer risks in overweight and obese individuals. The mechanistic pathways linking obesity status with adult chronic diseases such as cancer remain incompletely understood. A growing body of evidence suggests that novel approaches and interventional agents to disrupt the feed-forward cycle of maternal to offspring obesity transfer that is initiated in utero will be important for stemming both the obesity pandemic and the associated increase in cancer incidence. The convergence of multiple research areas including those encompassing the insulin and insulin-like growth factor systems, epigenetics, and stem cell biology is providing insights into the potential for cancer prevention in adult offspring previously exposed to the intrauterine environment of overweight/obese mothers. Here, we review the current state of this nascent research field, with a focus on three major cancers, namely breast, colorectal, and liver, and suggest some possible future directions to optimize its impact for the health of future generations.

Changes in diet and lifestyle and long-term weight gain in women and men

BACKGROUND

Specific dietary and other lifestyle behaviors may affect the success of the straightforward-sounding strategy "eat less and exercise more" for preventing long-term weight gain.

METHODS

We performed prospective investigations involving three separate cohorts that included 120,877 U.S. women and men who were free of chronic diseases and not obese at baseline, with follow-up periods from 1986 to 2006, 1991 to 2003, and 1986 to 2006. The relationships between changes in lifestyle factors and weight change were evaluated at 4-year intervals, with multivariable adjustments made for age, baseline body-mass index for each period, and all lifestyle factors simultaneously. Cohort-specific and sex-specific results were similar and were pooled with the use of an inverse-variance-weighted meta-analysis.

RESULTS

Within each 4-year period, participants gained an average of 3.35 lb (5th to 95th percentile, -4.1 to 12.4). On the basis of increased daily servings of individual dietary components, 4-year weight change was most strongly associated with the intake of potato chips (1.69 lb), potatoes (1.28 lb), sugar-sweetened beverages (1.00 lb), unprocessed red meats (0.95 lb), and processed meats (0.93 lb) and was inversely associated with the intake of vegetables (-0.22 lb), whole grains (-0.37 lb), fruits (-0.49 lb), nuts (-0.57 lb), and yogurt (-0.82 lb) (P≤0.005 for each comparison). Aggregate dietary changes were associated with substantial differences in weight change (3.93 lb across quintiles of dietary change). Other lifestyle factors were also independently associated with weight change (P<0.001), including physical activity (-1.76 lb across quintiles); alcohol use (0.41 lb per drink per day), smoking (new quitters, 5.17 lb; former smokers, 0.14 lb), sleep (more weight gain with <6 or >8 hours of sleep), and television watching (0.31 lb per hour per day).

CONCLUSIONS

Specific dietary and lifestyle factors are independently associated with long-term weight gain, with a substantial aggregate effect and implications for strategies to prevent obesity. (Funded by the National Institutes of Health and others.).

Excess body weight and obesity--the link with gastrointestinal and hepatobiliary cancer

Excess body weight (EBW) is an independent risk factor for many human malignancies, including cancers throughout the gastrointestinal and hepatobiliary tract from the esophagus to the colorectum. The relative risk of gastrointestinal cancer in obese individuals is approximately 1.5-2.0 times that for normal weight individuals, with organ-specific and gender-specific differences for specific cancers. The association between EBW and risk of premalignant stages of gastrointestinal carcinogenesis, such as colorectal adenoma and Barrett esophagus, is similar, implying a role for EBW during the early stages of carcinogenesis that could be relevant to preventative strategies. EBW also impacts negatively on gastrointestinal cancer outcomes. The mechanistic basis of the association between EBW and carcinogenesis remains incompletely understood. Postulated mechanisms include increased insulin and insulin-like growth factor signaling and chronic inflammation (both linked to the metabolic syndrome), as well as signaling via adipokines, such as leptin. The role of obesity-related changes in the intestinal microbiome in gastrointestinal carcinogenesis deserves further attention. Whether weight loss leads to reduced future gastrointestinal and liver cancer risk has yet to be fully explored. There is some support for the idea that weight loss negatively regulates colorectal carcinogenesis. In addition, data suggest a reduction in risk of several cancers in the first 10 years after bariatric surgery.

Self-reported and measured anthropometric data and risk of colorectal cancer in the EPIC-Norfolk study

BACKGROUND

Epidemiological studies have shown inconsistent results for the association between body size and colorectal cancer (CRC) risk. Inconsistencies may be because of the reliance on self-reported measures of body size.

OBJECTIVE

We examined the association of self-reported and directly assessed anthropometric data (body height, weight, body mass index (BMI), waist, hip, waist-to-hip ratio (WHR) and chest circumference) with CRC risk in the EPIC-Norfolk study.

DESIGN

A total of 20,608 participants with complete self-reported and measured height and weight and without any history of cancer were followed up an average of 11 years, during which 357 incident CRC cases were recorded. Hazard Ratios (HRs) and 95% confidence intervals (CIs) were estimated using Cox proportional hazards models.

RESULTS

After adjustment for confounders, HRs among women in the highest quintile of the body size measure relative to the lowest quintile showed that measured height (HR=1.98, 95% CI=1.19-3.28, P (trend)=0.009), measured waist circumference (HR=1.65, 95% CI=0.97-2.86, P (trend)=0.009) and measured WHR (HR=2.07, 95% CI=1.17-3.67, P (trend)=0.001) were associated with increased CRC risk. Associations using corresponding self-reported measures were attenuated and not statistically significant. Conversely, the association of BMI with CRC risk in women was weaker using measured BMI (HR=1.57, 95% CI=0.91-2.73, P (trend)=0.05) compared with self-reported BMI (HR=1.97, 95% CI=1.18-3.30, P (trend)=0.02). In men no significantly increased CRC risk was observed with any of the anthropometric measures.

CONCLUSIONS

Measured height, waist circumference and WHR were associated with CRC risk in women, whereas any significant associations with those measures were attenuated when self-reported data were used.

Reverse causation and illness-related weight loss in observational studies of body weight and mortality

In studies of weight and mortality, the construct of reverse causation has come to be used to imply that the exposure-outcome relation is biased by weight loss due to preexisting illness. Observed weight-mortality associations are sometimes thought to result from this bias. Evidence for the occurrence of such bias is weak and inconsistent, suggesting that either the analytical methods used have been inadequate or else illness-related weight loss is not an important source of bias. Deleting participants has been the most frequent approach to control possible bias. As implemented, this can lead to deletion of almost 90% of all deaths in a sample and to deletion of more overweight and obese participants than participants with normal or below normal weight. Because it has not been demonstrated that the procedures used to adjust for reverse causation increase validity or have large or systematic effects on relative risks, it is premature to consider reverse causation as an important cause of bias. Further research would be useful to elucidate the potential effects and importance of reverse causation or illness-related weight loss as a source of bias in the observed associations between weight and mortality in cohort studies.

Anthropometric factors in adulthood and risk of colorectal adenomas: The French E3N-EPIC prospective cohort

Anthropometric factors have been associated with colorectal cancer and adenomas but with conflicting results in women or regarding adenoma characteristics. The authors aimed to explore associations between anthropometric factors (height, weight, body mass index, waist and hip circumferences, and weight changes) and adenoma risk. They analyzed the 17,391 women of the French Etude épidémiologique des femmes de la Mutuelle Générale de l'Education Nationale (E3N)-European Prospective Investigation into Cancer and Nutrition (EPIC) cohort who underwent a colonoscopy during follow-up (1993-2002), including 1,408 who developed a first colorectal adenoma. In Cox multivariate proportional hazard regression models, obesity was associated with an increased colorectal adenoma risk (hazard ratio = 1.53, 95% confidence interval: 1.21, 1.94). This association was restricted to left colon adenomas (P(homogeneity) = 0.05 and 0.01 for colon vs. rectum and right vs. left colon, respectively), with a dose-effect relation observed from 22 kg/m². A high waist circumference was also associated with left colon adenoma risk (hazard ratio = 1.81, 95% confidence interval: 1.36, 2.41). Mean weight gain over 0.5 kg/year was associated with a 23% increased colorectal adenoma risk. Associations did not differ between advanced and nonadvanced adenomas. In conclusion, study findings suggest that obesity and weight gain are associated with early colorectal carcinogenesis in women, and specifically regarding the distal colon.