Is weight loss beneficial for reduction of morbidity and mortality? What is the controversy about?

Maternal BMI changes from the prepregnancy to postpartum period are associated with postpartum cardiometabolic risk factors: a longitudinal study

PURPOSE

This study aimed at investigating the associations between the total body mass index (BMI) change at 3 or 4 years postpartum compared to the prepregnancy and cardiometabolic risk factors.

METHODS

This longitudinal study included 1305 participants. Based on the total postpartum BMI changes, they were divided into < 0 units, 0-1.7 units, and > 1.7 units groups using the interquartile range. Multiple linear regression models were used to analyze the associations.

RESULTS

Compared to the reference group, there was a progressive increase in the βcoefficient (βcoef) of homeostasis model assessment of insulin resistance (HOMA-IR) of cardiometabolic risk in the following groups: the '0-1.7 units' group with the 'overweight traj' [βcoef 0.33; 95% confidence intervals (CI) 0.22, 0.44)] or the 'obesity traj' [0.66; (0.45, 0.88)] and the '> 1.7 units' group with the 'normal traj' [0.33; (0.22, 0.44)], the 'overweight traj' [0.54; (0.41, 0.67)] or the 'obesity traj' [0.97; (0.79, 1.15)]. The same increasing trend of βcoef was also found in DBP, FPG, LDL, WHR, BF%. However, the '< 0 units' group with the 'low traj' [0.13; (0.06, 0.21)] and the '0-1.7 units' group with the 'low traj' [0.08; (0.03, 0.13)] had higher high-density lipoprotein cholesterol (HDL-C) level than the reference group.

CONCLUSION

Women with a postpartum BMI gain > 1.7 units are positively associated with cardiometabolic risk factors, especially for those in the 'obesity traj' or 'traj D'. Conversely, women with a postpartum BMI loss > 0 units have negative association with cardiometabolic risk factors, especially for those in the 'low traj' or 'traj B'.

'Weighing' Losses and Gains: Evaluation of the Healthy Lifestyle Modification After Breast Cancer Pilot Program

Objectives

This pilot study sought to develop and evaluate a novel online group-based intervention (Healthy Lifestyle Modification after Breast Cancer; HLM-ABC) to help breast cancer survivors (BCSs) make healthy lifestyle changes intended to yield not only beneficial physical outcomes (i.e., weight loss, reduced body mass index) but also greater behavioral (e.g., increased physical activity, healthier eating), and psychosocial well-being (e.g., self-efficacy, motivation, body image).

Methods

An exploratory single-arm, mixed-method triangulation design was employed to evaluate the feasibility and preliminary effectiveness of the HLM-ABC intervention for overweight BCSs. Fourteen women participated in the 10-week intervention and completed quantitative measures of the above-mentioned outcomes at baseline, post-treatment, 6-month, and 12-month follow-up time points. Qualitative data were obtained post-treatment via semi-structured interviews and a treatment satisfaction questionnaire.

Results

Participants lost an average of 2.83% of their baseline weight (M = 196.65; SD = 38.59) by 1-year follow-up (M = 191.29; SD = 33.91), equal to a small effect size (d = -0.37). Despite achieving only modest weight loss, participants achieved meaningful gains in the form of increased physical activity (d = 0.2), discovery of gratifying movement, more intuitive eating habits (d = 1.12), greater bodily and emotional awareness, and positive shifts in beliefs about being able to make healthy choices regarding food (d = 0.63) and physical activity (d = 0.38). Furthermore, they demonstrated a slight improvement in body image (d = 0.36) and described feeling more self-compassionate, empowered, and acknowledging of variables beyond control (i.e., hormonal therapy, unsatisfactory surgery) that can present barriers to change.

Conclusion

After completing a 10-week online program, participants achieved meaningful and lasting changes on a number of healthful indicators, even when this did not correspond with a significant reduction in weight. Findings highlight the complex, multifaceted nature of "health" and lend support for promotion of healthier lifestyle following cancer treatment that encompasses not only physical weight, but also behavior, psychosocial well-being, and (often unmodifiable) circumstances such as life-preserving hormonal treatments.

Five-Year Change in Body Mass Index Predicts Conversion to Mild Cognitive Impairment or Dementia Only in APOE ɛ4 Allele Carriers

BACKGROUND

Body mass index (BMI) has been identified as an important modifiable lifestyle risk factor for dementia, but less is known about how BMI might interact with Apolipoprotein E ɛ4 (APOE ɛ4) carrier status to predict conversion to mild cognitive impairment (MCI) and dementia.

OBJECTIVE

The aim of this study was to investigate the interaction between APOE ɛ4 status and baseline (bBMI) and five-year BMI change (ΔBMI) on conversion to MCI or dementia in initially cognitively healthy older adults.

METHODS

The associations between bBMI, ΔBMI, APOE ɛ4 status, and conversion to MCI or dementia were investigated among 1,289 cognitively healthy elders from the National Alzheimer's Coordinating Center (NACC) database.

RESULTS

After five years, significantly more carriers (30.6%) converted to MCI or dementia than noncarriers (17.6%), p < 0.001, OR = 2.06. Neither bBMI (OR = 0.99, 95%CI = 0.96-1.02) nor the bBMI by APOE interaction (OR = 1.02, 95%CI = 0.96-1.08) predicted conversion. Although ΔBMI also did not significantly predict conversion (OR = 0.90, 95%CI = 0.78-1.04), the interaction between ΔBMI and carrier status was significant (OR = 0.72, 95%CI = 0.53-0.98). For carriers only, each one-unit decline in BMI over five years was associated with a 27%increase in the odds of conversion (OR = 0.73, 95%CI = 0.57-0.94).

CONCLUSION

A decline in BMI over five years, but not bBMI, was strongly associated with conversion to MCI or dementia only for APOE ɛ4 carriers. Interventions and behaviors aimed at maintaining body mass may be important for long term cognitive health in older adults at genetic risk for AD.

Effect of late-life weight change on dementia incidence: a 10-year cohort study using claim data in Korea

BACKGROUND

The association between body mass index (BMI) in late-life and dementia risk remains unclear. We investigated the association between BMI changes over a 2-year period and dementia in an elderly Korean population.

METHODS

We examined 67 219 participants aged 60-79 years who underwent BMI measurement in 2002/2003 and 2004/2005 as part of the National Health Insurance Service-Health Screening Cohort. Baseline characteristics including BMI, socioeconomic status and cardiometabolic risk factors were measured at baseline (2002/2003). The difference between BMI at baseline and at the next health screening (2004/2005) was used to calculate the BMI change. After 2 years, the incidence of dementia was monitored for a mean 5.3 years from 2008 to 2013. Multivariate HRs for dementia incidence were estimated on the basis of baseline BMI and its changes after adjusting for various other risk factors. A subgroup analysis was conducted to determine the effects of baseline BMI and BMI changes.

RESULTS

We demonstrated a significant association between late-life BMI changes and dementia in both sexes (men: >-10% HR=1.26, 95% CI 1.08 to 1.46, >+10% HR=1.25, 95% CI 1.08 to 1.45; women: >-10% HR=1.15, 95% CI 1.03 to 1.29, >+10% HR=1.17, 95% CI 1.05 to 1.31). However, the baseline BMI was not associated with dementia, except in underweight men. After stratification based on the baseline BMI, the BMI increase over 2 years was associated with dementia in men with a BMI of <25 kg/m² and women with a BMI of 18.5-25 kg/m², but not in the obese subgroup in either sex. However, BMI decrease was associated with dementia in those with a BMI of ≥18.5 kg/m², but not in the underweight subgroup in either sex.

CONCLUSION

Both weight gain and weight loss may be significant risk factors associated with dementia. Continuous weight control and careful monitoring of weight changes are necessary to prevent dementia development.

Observational Evidence for Unintentional Weight Loss in All-Cause Mortality and Major Cardiovascular Events: A Systematic Review and Meta-Analysis

The obesity paradox has been described in several observational cohorts and meta-analysis. However, evidence of the intentionality of weight loss in all-cause deaths and major cardiovascular events (MACE) in prospective cohorts is unclear. We analysed whether involuntary weight loss is associated with increased cardiovascular events and mortality. In a systematic review, we searched multiple electronic databases for observational studies published up to October 2016. Studies reporting risk estimates for unintentional weight loss compared with stable weight in MACE and mortality were included. Fifteen studies met the selection criteria, with a total of 178,644 participants. For unintentional weight loss, we found adjusted risk ratios (RRs) with confidence intervals (CIs) of 1.38 (95% CI: 1.23, 1.53) and 1.17 (95% CI: 0.98, 1.37) for all-cause mortality and MACE, respectively. Participants with comorbidities, overweight and obese populations, and older adults yielded RRs (95% CI) of 1.49 (1.30, 1.68), 1.11 (1.04, 1.18), and 1.81 (1.59, 2.03), respectively. Unintentional weight loss had a significant impact on all-cause mortality. We found no protective effect of being overweight or obese for unintentional weight loss and MACE.

Effects of Initial Body Mass Index and Weight Change on All-Cause Mortality: A 10-Year Cohort Study in Korea

We evaluated the effects of baseline body mass index (BMI) and its changes over 4 years on all-cause mortality in Korean population. We analyzed 351 735 participants whose BMI was measured in both 2002/2003 and 2006/2007. Mortality was assessed until 2013. Multivariate hazard ratios for all-cause mortality were estimated. Underweight and severe obesity with BMI >30 kg/m2 were significantly associated with higher mortality. Similarly, >5% decrease or >10% increase of BMI for 4 years was associated with the increased risk of death. Comparing the results between baseline BMI and BMI change, the BMI change showed more stable associations with mortality than the baseline BMI in subgroup analysis such as nonsmokers and healthy participants. This study suggests that BMI change could be a useful health indicator along with obesity level by BMI. In addition, maintaining a healthy weight is needed for longevity, but rapid weight change should be carefully monitored.

Estimating the lifetime cost of childhood obesity in Germany: Results of a Markov Model

BACKGROUND

Child obesity is a growing public health concern. Excess weight in childhood is known to be associated with a high risk of obesity and obesity-related comorbidities in adulthood.

OBJECTIVES

This study quantifies lifetime excess costs of overweight and obese adults in Germany taking the history of obesity in childhood into account.

METHODS

A two-stage Markov cohort state transition model was developed. At stage 1, the distribution of body mass index (BMI) categories was tracked from childhood (ages 3-17) to adulthood (age 17 and up). Based on these results, it was distinguished whether adults had been normal in weight or overweight/obese as child. At stage 2, age-specific and lifetime costs from age 18 onwards were simulated in two further Markov cohort models, one for each of the two BMI groups. Model parameter values were obtained from the German Interview and Examination Survey for Children and Adolescents (KiGGS), the German Microcensus 2009 and published literature.

RESULTS

When compared with normal weight adults, lifetime excess costs are higher among adults who had been overweight or obese at any point during childhood. For 18-year-old women (men), who have been overweight/obese during their childhood (ages 3-17), undiscounted lifetime excess costs are estimated at €19,479 (€14,524), with 60% (67%) occurring beyond age 60. Discounted (3%) lifetime excess costs are considerably lower, amounting to €4262 for men and €7028 for women.

CONCLUSIONS

Because childhood obesity determines healthcare costs occurring in adulthood, interventions preventing the persistence of child obesity and obesity-related comorbidities during adulthood could have a substantial impact on reducing the burden of the obesity epidemic.

Changes in body mass index, waist and hip circumferences, waist to hip ratio and risk of all-cause mortality in men

BACKGROUND

There is a paucity of data about the impact of changes in anthropometric measurements on the risk of mortality events, especially in men.

METHODS

The study sample consists of 1805 Iranian men, aged ⩾ 30 years, free from cardiovascular disease at baseline; they had undergone health examinations in both phases I (1999-2001) and II (2001-2003) and were followed up until March 2010. Participants were categorized by changes in anthropometric measurements into four groups: Group 1, change percentage<-5%; Group 2, -5% ⩽ change percentages<+5%; Group 3, 5% ⩽ change percentage<10%; and Group 4, change percentage ⩾ 10%. Cox proportional hazard regression was performed to assess the hazard ratios (HRs) of the anthropometric changes for all-cause mortality, given group 2 as the reference.

RESULTS

During 6.6 years of follow-up, 88 cases of mortality events occurred. The confounder-adjusted multivariate HRs for the first, third and fourth groups of hip circumference (HC) changes were 3.13(1.28-7.64), 0.75(0.43-1.31) and 0.82(0.23-2.99); the corresponding values for waist to hip ratio (WHR) change were 1.80(0.75-4.33), 1.21(0.70-2.1) and 2.32(1.25-4.3). After further adjustment for mediator covariates, results did not change. The equivalent values for body mass index and waist circumference did not reach statistical significance.

CONCLUSIONS

In Middle Eastern Caucasian men, increase in WHR was associated with incident mortality, which was more prominent in those with ⩾ 10% increase in the ratio. Moreover, decrease in HC was highly associated with excess risk of mortality.

The weight-inclusive versus weight-normative approach to health: evaluating the evidence for prioritizing well-being over weight loss

Using an ethical lens, this review evaluates two methods of working within patient care and public health: the weight-normative approach (emphasis on weight and weight loss when defining health and well-being) and the weight-inclusive approach (emphasis on viewing health and well-being as multifaceted while directing efforts toward improving health access and reducing weight stigma). Data reveal that the weight-normative approach is not effective for most people because of high rates of weight regain and cycling from weight loss interventions, which are linked to adverse health and well-being. Its predominant focus on weight may also foster stigma in health care and society, and data show that weight stigma is also linked to adverse health and well-being. In contrast, data support a weight-inclusive approach, which is included in models such as Health at Every Size for improving physical (e.g., blood pressure), behavioral (e.g., binge eating), and psychological (e.g., depression) indices, as well as acceptability of public health messages. Therefore, the weight-inclusive approach upholds nonmaleficience and beneficience, whereas the weight-normative approach does not. We offer a theoretical framework that organizes the research included in this review and discuss how it can guide research efforts and help health professionals intervene with their patients and community.

Look inside Look AHEAD: why the glass is more than half-full

Look AHEAD is the only long-term study in a large cohort of subjects with type 2 diabetes that assessed the effect of intensive lifestyle, predominantly diet and exercise, on a number of outcomes. While Look AHEAD was not able to detect a significant effect of intensive lifestyle modification on cardiovascular outcomes, it clearly demonstrated numerous beneficial and sustained effects on health outcomes that are relevant to this population. Without the exceptional retention of study participants, it would have been difficult to detect these benefits. Our review provides a perspective on aspects related to exercise, diet, and weight loss in relation to cardiovascular outcomes and potential future research.

Changes in health behaviors and their associations with depressive symptoms among Israelis aged 50+

OBJECTIVE

To examine the longitudinal association between changes in health behaviors and depression and determine the mediating effect of health characteristics on this association.

METHOD

Based on the first and second waves of the Survey of Health, Aging and Retirement in Europe (SHARE)-Israel, depressive symptoms of 1,524 Israelis aged 50 or older were analyzed using logistic regression.

RESULTS

Changes in physical activity and body weight are associated with depressive symptoms after adjusting for confounders. However, after adding measures of health, the respective correlations of weight gain and commenced physical activity with depression disappear, and the correlation between continued activity and depression is reduced.

DISCUSSION

Changes in health behaviors are related to mental health in late life, but their effect is mediated by physical and functional health. Future interventions should nevertheless target older individuals who stop physical activity and those who remain inactive to lessen the risk of depression.

Keap1-knockdown decreases fasting-induced fatty liver via altered lipid metabolism and decreased fatty acid mobilization from adipose tissue

AIMS

The purpose of this study was to determine whether Nrf2 activation, via Keap1-knockdown (Keap1-KD), regulates lipid metabolism and mobilization induced by food deprivation (e.g. fasting).

METHODS AND RESULTS

Male C57BL/6 (WT) and Keap1-KD mice were either fed ad libitum or food deprived for 24 hours. After fasting, WT mice exhibited a marked increase in hepatic lipid accumulation, but Keap1-KD mice had an attenuated increase of lipid accumulation, along with reduced expression of lipogenic genes (acetyl-coA carboxylase, stearoyl-CoA desaturase-1, and fatty acid synthase) and reduced expression of genes related to fatty acid transport, such as fatty acid translocase/CD36 (CD36) and Fatty acid transport protein (FATP) 2, which may attribute to the reduced induction of Peroxisome proliferator-activated receptor (Ppar) α signaling in the liver. Additionally, enhanced Nrf2 activity by Keap1-KD increased AMP-activated protein kinase (AMPK) phosphorylation in liver. In white adipose tissue, enhanced Nrf2 activity did not change the lipolysis rate by fasting, but reduced expression of fatty acid transporters--CD36 and FATP1, via a PPARα-dependent mechanism, which impaired fatty acid transport from white adipose tissue to periphery circulation system, and resulted in increased white adipose tissue fatty acid content. Moreover, enhanced Nrf2 activity increased glucose tolerance and Akt phosphorylation levels upon insulin administration, suggesting Nrf2 signaling pathway plays a key role in regulating insulin signaling and enhanced insulin sensitivity in skeletal muscle.

CONCLUSION

Enhanced Nrf2 activity via Keap1-KD decreased fasting-induced steatosis, pointing to an important function of Nrf2 on lipid metabolism under the condition of nutrient deprivation.

Changes in body mass index following newly diagnosed type 2 diabetes and risk of cardiovascular mortality: a cohort study of 8486 primary-care patients

AIMS

Elevated body mass index (BMI) is associated with an increased risk of type 2 diabetes and cardiovascular disease (CVD). This study explored the association between BMI changes in the first 18 months of newly diagnosed type 2 diabetes and the risk of long-term CVD mortality.

METHODS

A total of 8486 patients with newly diagnosed type 2 diabetes and no previous history of CVD or cancer were identified from 84 primary-care centres in Sweden. During the first year after diagnosis, patients were grouped according to BMI change: 'Increase', or ≥+1 BMI unit; 'unchanged', or between +1 and-1 BMI unit; and 'decrease', or ≤-1 BMI unit. Associations between BMI change and CVD mortality, defined as death from stroke, myocardial infarction or sudden death, were estimated using adjusted Cox proportional hazards models (NCT 01121315).

RESULTS

Baseline mean age was 60.0 years and mean BMI was 30.2kg/m(2). Patients were followed for up to 9 years (median: 4.6 years). During the first 18 months, 53.4% had no change in their BMI, while 32.2% decreased and 14.4% increased. Compared with patients with unchanged BMI, those with an increased BMI had higher risks of CVD mortality (hazard ratio: 1.63, 95% CI: 1.11-2.39) and all-cause mortality (1.33, 1.01-1.76). BMI decreases had no association with these risks compared with unchanged BMI: 1.06 (0.76-1.48) and 1.06 (0.85-1.33), respectively.

CONCLUSION

Increased BMI within the first 18 months of type 2 diabetes diagnosis was associated with an increased long-term risk of CVD mortality. However, BMI decrease did not lower the long-term risk of mortality.

Beneficial effect of dietary Ephedra sinica on obesity and glucose intolerance in high-fat diet-fed mice

Obesity is a major contributor to both glucose intolerance and metabolic syndrome. In this study, we investigated the anti-obesity and anti-hyperglycemic effects of Ephedra sinica on high-fat diet-fed mice. Male ICR mice were divided into four groups; the normal group, the obese and diabetic control group treated with a high-fat diet, the positive control group treated with a high-fat diet containing acarbose, and the experimental group treated with a high-fat diet containing Ephedra sinica. The effects of Ephedra sinica on obesity and glucose intolerance were measured by an oral glucose tolerance test (OGTT), plasma biochemistry, body and epididymal fat weight; the expression of adiponectin, peroxisome-proliferator-activated receptor α (PPAR-α), tumor necrosis factor α (TNF-α) and leptin was also determined. Ephedra sinica reduced weight gain and epididymal fat accumulation, improved glucose intolerance on the OGTT, decreased triglycerides and increased high-density lipoprotein cholesterol compared to the controls. Moreover, it reduced weight gain and fasting glucose levels and improved HDL-cholesterol levels more than acarbose. Gene expression analysis revealed that Ephedra sinica upregulated the expression of adiponectin and PPAR-α, and downregulated the expression of TNF-α. From these results, we suggest that Ephedra sinica may reduce obesity and hyperglycemia by increasing PPAR-α and adiponectin and reducing TNF-α, and that it may have the potential to be used clinically as an ingredient in food or drugs effective in obesity-related glucose intolerance treatments.

Dose-dependent effects of the once-daily GLP-1 receptor agonist lixisenatide in patients with Type 2 diabetes inadequately controlled with metformin: a randomized, double-blind, placebo-controlled trial

AIMS

To evaluate the dose-response relationship of lixisenatide (AVE0010), a glucagon-like peptide-1 (GLP-1) receptor agonist, in metformin-treated patients with Type 2 diabetes.

METHODS

Randomized, double-blind, placebo-controlled, parallel-group, 13 week study of 542 patients with Type 2 diabetes inadequately controlled [glycated haemoglobin (HbA(1c)) > or = 7.0 and < 9.0% (> or = 53 and < 75 mmol/mol)] on metformin (> or = 1000 mg/day) treated with subcutaneous lixisenatide doses of 5, 10, 20 or 30 microg once daily or twice daily or placebo. The primary end-point was change in HbA(1c) from baseline to 13 weeks in the intent-to-treat population.

RESULTS

Lixisenatide significantly improved mean HbA(1c) from a baseline of 7.55% (59.0 mmol/mol); respective mean reductions for 5, 10, 20 and 30 microg doses were 0.47, 0.50, 0.69 and 0.76% (5.1, 5.5, 7.5 and 8.3 mmol/mol), on once-daily and 0.65, 0.78, 0.75 and 0.87% (7.1, 8.5, 8.2 and 9.5 mmol/mol) on twice-daily administrations vs. 0.18% (2.0 mmol/mol) with placebo (all P < 0.01 vs. placebo). Target HbA(1c) < 7.0% (53 mmol/mol) at study end was achieved in 68% of patients receiving 20 and 30 microg once-daily lixisenatide vs. 32% receiving placebo (P < 0.0001). Dose-dependent improvements were observed for fasting, postprandial and average self-monitored seven-point blood glucose levels. Weight changes ranged from -2.0 to -3.9 kg with lixisenatide vs. -1.9 kg with placebo. The most frequent adverse event was mild-to-moderate nausea.

CONCLUSIONS

Lixisenatide significantly improved glycaemic control in mildly hyperglycaemic patients with Type 2 diabetes on metformin. Dose-response relationships were seen for once- and twice-daily regimens, with similar efficacy levels, with a 20 microg once-daily dose of lixisenatide demonstrating the best efficacy-to-tolerability ratio. This new, once-daily GLP-1 receptor agonist shows promise in the management of Type 2 diabetes to be defined further by ongoing long-term studies.

Pathophysiological analysis of female Spontaneously Diabetic Torii fatty rats

Obesity, hyperglycemia, hyperlipidemia, and diabetes-associated complications appear at younger ages (6-8 weeks) in the male Spontaneously Diabetic Torii-Lepr(fa) (SDT-fa/fa) rat than in the male original SDT (SDT-+/+) rat. However, the incidence and progression of diabetes mellitus and diabetic complications in the female SDT-fa/fa rat have not been reported in detail. In the present study, the pathophysiological features of the female SDT-fa/fa rat were examined, and compared with those of the female SDT-+/+ rat. Female SDT-fa/fa rats showed hyperphagia, obesity, hyperglycemia, and hyperlipidemia from 5 or 6 weeks of age, and hyperinsulinemia was observed from 5 to 12 weeks. Pathological changes pancreatic islets were observed from 8 weeks. Renal function parameters, such as urine volume and urinary protein, increased from 16 weeks, and pathological findings in the renal tubule, and cataracts were also observed from 16 weeks. Increases of visceral and subcutaneous fats were obvious during the observation period. In pair-feeding with SDT-+/+ rats, SDT-fa/fa rats showed improved hyperglycemia and hypertriglycemia, but hypercholesterolemia was not entirely improved during the study period. Female SDT-fa/fa rats showed diabetes mellitus and diabetes-associated complications at young ages, and fat accumulation was remarkable. Suppression of hyperphagia in SDT-fa/fa rats was effective at improving hyperglycemia and hypertriglycemia. In conclusion, the female SDT-fa/fa rat has the potential to become an important animal model of type 2 diabetes mellitus with obesity, especially for women, for which few models currently exist.

A review and meta-analysis of the effect of weight loss on all-cause mortality risk

Overweight and obesity are associated with increased morbidity and mortality, although the range of body weights that is optimal for health is controversial. It is less clear whether weight loss benefits longevity and hence whether weight reduction is justified as a prime goal for all individuals who are overweight (normally defined as BMI>25 kg/m2). The purpose of the present review was to examine the evidence base for recommending weight loss by diet and lifestyle change as a means of prolonging life. An electronic search identified twenty-six eligible prospective studies that monitored subsequent mortality risk following weight loss by lifestyle change, published up to 2008. Data were extracted and further analysed by meta-analysis, giving particular attention to the influence of confounders. Moderator variables such as reason for weight loss (intentional, unintentional), baseline health status (healthy, unhealthy), baseline BMI (normal, overweight, obese), method used to estimate weight loss (measured weight loss, reported weight loss) and whether models adjusted for physical activity (adjusted data, unadjusted data) were used to classify subgroups for separate analysis. Intentional weight loss per se had a neutral effect on all-cause mortality (relative risk (RR) 1·01; P = 0·89), while weight loss which was unintentional or ill-defined was associated with excess risk of 22 to 39 %. Intentional weight loss had a small benefit for individuals classified as unhealthy (with obesity-related risk factors) (RR 0·87 (95 % CI 0·77, 0·99); P = 0·028), especially unhealthy obese (RR 0·84 (95 % CI 0·73, 0·97); P = 0·018), but appeared to be associated with slightly increased mortality for healthy individuals (RR 1·11 (95 % CI 1·00, 1·22); P = 0·05), and for those who were overweight but not obese (RR 1·09 (95 % CI 1·02, 1·17); P = 0·008). There was no evidence for weight loss conferring either benefit or risk among healthy obese. In conclusion, the available evidence does not support solely advising overweight or obese individuals who are otherwise healthy to lose weight as a means of prolonging life. Other aspects of a healthy lifestyle, especially exercise and dietary quality, should be considered. However, well-designed intervention studies are needed clearly to disentangle the influence of physical activity, diet strategy and body composition, in order to define appropriate advice to those populations that might be expected to benefit.