Forecasting the obesity epidemic in the aging U.S. population

Forecasting the effects of obesity and smoking on U.S. life expectancy

BACKGROUND

Although increases in obesity over the past 30 years have adversely affected the health of the U.S. population, there have been concomitant improvements in health because of reductions in smoking. Having a better understanding of the joint effects of these trends on longevity and quality of life will facilitate more efficient targeting of health care resources.

METHODS

For each year from 2005 through 2020, we forecasted life expectancy and quality-adjusted life expectancy for a representative 18-year-old, assuming a continuation of past trends in smoking (based on data from the National Health Interview Survey for 1978 through 1979, 1990 through 1991, 1999 through 2001, and 2004 through 2006) and past trends in body-mass index (BMI) (based on data from the National Health and Nutrition Examination Survey for 1971 through 1975, 1988 through 1994, 1999 through 2002, and 2003 through 2006). The 2003 Medical Expenditure Panel Survey was used to examine the effects of smoking and BMI on health-related quality of life.

RESULTS

The negative effects of increasing BMI overwhelmed the positive effects of declines in smoking in multiple scenarios. In the base case, increases in the remaining life expectancy of a typical 18-year-old are held back by 0.71 years or 0.91 quality-adjusted years between 2005 and 2020. If all U.S. adults became nonsmokers of normal weight by 2020, we forecast that the life expectancy of an 18-year-old would increase by 3.76 life-years or 5.16 quality-adjusted years.

CONCLUSIONS

If past obesity trends continue unchecked, the negative effects on the health of the U.S. population will increasingly outweigh the positive effects gained from declining smoking rates. Failure to address continued increases in obesity could result in an erosion of the pattern of steady gains in health observed since early in the 20th century.

Getting heavier, younger: trajectories of obesity over the life course

Context

Although recent trends in obesity have been well documented, generational patterns of obesity from early childhood through adulthood across birth cohorts, which account for the recent epidemic of childhood obesity, have not been well described. Such trends may have implications for the prevalence of obesity-associated conditions among population subgroups, including type 2 diabetes.

Objective

Our objective was to evaluate trajectories of obesity over the life course for the US population, overall and by gender and race.

Design, Setting, and Participants

We conducted an age, period, and birth cohort analysis of obesity for US individuals who participated in the National Health and Nutrition Examination Surveys (1971-2006).

Main Outcome Measures

Obesity was defined as a body mass index ≥ 95th percentile for individuals aged 2-16 years or ≥ 30 kg/m2 among individuals older than 16 years. Age was represented by the age of the individual at each NHANES survey, period was defined by the year midpoint of each survey, and cohort was calculated by subtracting age from period.

Results

Recent birth cohorts are becoming obese in greater proportions for a given age, and are experiencing a greater duration of obesity over their lifetime. For example, whereas the 1966-75 and 1976-85 birth cohorts had reached an estimated obesity prevalence of at least 20% by 20-29 years of age, this level was only reached by 30-39 years for the 1946-55 and 1956-65 birth cohorts, by 40-49 years for the 1936-45 birth cohort, and by 50-59 years of age for the 1926-35 birth cohort. Trends are particularly pronounced for female compared with male, and black compared with white cohorts.

Conclusions

The increasing cumulative exposure to excess weight over the lifetime of recent birth cohorts will likely have profound implications for future rates of type 2 diabetes, and mortality within the US population.

Trends in Americans’ food-related time use: 1975–2006

Objective

To describe how the time spent in food-related activities by Americans has changed over the past 30 years.

Design

Data from four national time diary surveys, spanning 1975–2006, are used to construct estimates of trends in American adults’ time spent in food-related activities. Multivariate Tobits assess how food-related activities have changed over time controlling for sociodemographic and economic covariates.

Results

Both bivariate and multivariate estimates reveal that between 1975 and 2006, American women’s time spent in food preparation declined substantially, whereas the time spent in these activities by American men changed very little. On the contrary, grocery shopping time increased modestly for both men and women. The primary eating time (i.e. time when eating/drinking was the respondent’s main focus) declined for both men and women over this historical period, and the composition of this time changed with less primary eating time being done alone. Concurrently, secondary eating time (i.e. time when something else had the respondent’s primary attention, but eating/drinking simultaneously occurred) rose precipitously for both women and men between 1975 and 1998.

Conclusions

The total time spent in eating (i.e. primary plus secondary eating time) has increased over the past 30 years, and the composition of this time has shifted from situations in which energy intake can be easily monitored to those in which energy intake may be more difficult to gauge. Less time is also being spent in food preparation and clean-up activities. Future research should explore possible links between these trends and Americans’ growing obesity risk.

Joint association of obesity and metabolic syndrome with incident mobility limitation in older men and women--results from the Health, Aging, and Body Composition Study

BACKGROUND

Although both obesity and the metabolic syndrome (MetS) are known risk factors for decline in physical function, the joint association of obesity and metabolic alterations with risk of incident mobility limitation is unknown.

METHODS

Data are from 2,984 women and men aged 70-79 years participating in the Health, Aging, and Body Composition Study without mobility limitation at baseline. Obesity was defined as body mass index greater than or equal to 30 kg/m(2) and the MetS as meeting greater than or equal to 3 of the ATP III criteria. Mobility limitation was defined as any difficulty walking one-quarter mile or climbing 10 steps during two consecutive semiannual assessments for more than 6.5 years.

RESULTS

Incidence of mobility limitation was 55% in women and 44% in men. In women, adjusted risk of developing mobility limitation was progressively greater in nonobese participants with the MetS (hazard ratio [HR] = 1.49, 95% confidence interval [CI] = 1.24-1.80), obese participants without the MetS (HR = 1.95, 95% CI = 1.51-2.53), and obese participants with the MetS (HR = 2.16, 95% CI = 1.78-2.63) relative to the nonobese without the MetS. In men, the corresponding adjusted HRs (95% CI) were 1.07 (0.87-1.32), 1.64 (1.19-2.25), and 1.41 (1.12-1.78). Elevated inflammatory markers partly explained the association between obesity, the MetS, and mobility limitation, particularly in nonobese and obese participants with the MetS.

CONCLUSIONS

Obesity itself, independent of its metabolic consequences, is a risk factor for mobility limitation among obese older adults. In addition, having the MetS increases the risk of functional decline in older nonobese women but not in men.

Obesity accelerates thymic aging

As the expanding obese population grows older, their successful immunologic aging will be critical to enhancing the health span. Obesity increases risk of infections and cancer, suggesting adverse effects on immune surveillance. Here, we report that obesity compromises the mechanisms regulating T-cell generation by inducing premature thymic involution. Diet-induced obesity reduced thymocyte counts and significantly increased apoptosis of developing T-cell populations. Obesity accelerated the age-related reduction of T-cell receptor (TCR) excision circle bearing peripheral lymphocytes, an index of recently generated T cells from thymus. Consistent with reduced thymopoiesis, dietary obesity led to reduction in peripheral naive T cells with increased frequency of effector-memory cells. Defects in thymopoiesis in obese mice were related with decrease in the lymphoid-primed multipotent progenitor (Lin-Sca1+Kit+ Flt3+) as well as common lymphoid progenitor (Lin-Sca1+CD117(lo)CD127+) pools. The TCR spectratyping analysis showed that obesity compromised V-beta TCR repertoire diversity. Furthermore, the obesity induced by melanocortin 4 receptor deficiency also constricted the T-cell repertoire diversity, recapitulating the thymic defects observed with diet-induced obesity. In middle-aged humans, progressive adiposity with or without type 2 diabetes also compromised thymic output. Collectively, these findings establish that obesity constricts T-cell diversity by accelerating age-related thymic involution.

Effect of CLA isomers and their mixture on aging C57Bl/6J mice

BACKGROUND

Dietary supplements containing conjugated linoleic acid (CLA) are widely promoted for weight loss management over the counter. Recently, FDA approved the CLA as Generally Recognized as Safe category so that it can be used in various food and beverages. The combined effect of CLA isomers have been studied extensively in animals and humans, however, the role of individual isomers remains unraveled.

AIM

The present investigation addresses the effects of CLA isomers on body composition and body weight as well as safety using female C57Bl/6J aging mice.

METHODS

Two main CLA isomers and their mixture were fed to 12-months-old female C57Bl/6J mice. Ten percent corn oil (CO) based fat diet supplemented with 0.5% purified cis 9 trans 11 (c9,t11) CLA or trans 10 cis 12 (t10,c12) CLA or their mixture (CLA mix, 50:50) for 6 months. The lean mass, fat mass, glucose, non-esterified fatty acids, and insulin were examined at the end of study.

RESULTS

As a result of 6 months dietary intervention, both t10,c12 CLA and CLA mix groups showed increased lean mass and reduced fat mass compared to that of c9,t11 CLA and CO group. However, insulin resistance and liver hypertrophy were observed in t10,c12 CLA and CLA mix groups based on the results of homeostasis model assessment, revised quantitative insulin-sensitivity check index (R-QUICKI), intravenous glucose tolerance test, and liver histology. Liver histology revealed that increased liver weight was due to hypertrophy.

CONCLUSION

In conclusion, the major CLA isomers have a distinct effect on fat mass, glucose, and insulin metabolism. The t10,c12 isomer was found to reduce the fat mass and to increase the lean mass but significantly contributed to increase insulin resistance and liver hypertrophy, whereas c9,t11 isomer prevented the insulin resistance. Between the two major CLA isomers, the t10,c12 was attributed to reduce fat mass whereas, c9,t11 improves the insulin sensitivity.

The effect of obesity combined with low muscle strength on decline in mobility in older persons: results from the InCHIANTI study

OBJECTIVE

Both obesity and muscle impairment are increasingly prevalent among older persons and negatively affect health and physical functioning. However, the combined effect of coexisting obesity and muscle impairment on physical function decline has been little studied. We examined whether obese persons with low muscle strength experience significantly greater declines in walking speed and mobility than persons with only obesity or low muscle strength.

DESIGN

Community-dwelling adults aged > or = 65 years (n = 930) living in the Chianti geographic area (Tuscany, Italy) were followed for 6 years in the population-based InCHIANTI study.

MEASUREMENTS

On the basis of baseline measurements (1998-2000), obesity was defined as body mass index (BMI) > or = 30 kg/m(2) and low muscle strength as lowest sex-specific tertile of knee extensor strength. Walking speed and self-reported mobility disability (ability to walk 400 m or climb one flight of stairs) were assessed at baseline and at 3- and 6-year follow-up.

RESULTS

At baseline, obese persons with low muscle strength had significantly lower walking speed compared with all other groups (P < or = 0.05). In longitudinal analyses, obese participants with low muscle strength had steeper decline in walking speed and high risk of developing new mobility disability over the 6-year follow-up compared with those without obesity or low muscle strength. After the age of 80, the differences between groups were substantially attenuated. The differences seen in walking speed across combination of low muscle strength and obesity groups were partly explained by 6-year changes in muscle strength, BMI and waist circumference.

CONCLUSIONS

Obesity combined with low muscle strength increases the risk of decline in walking speed and developing mobility disability, especially among persons < 80 years old.

Impact of obesity on perioperative outcomes of minimally invasive esophagectomy

BACKGROUND

Abnormal body mass index has been targeted as a predictor of complications after major surgery. The aim of this study was to review the impact of obesity on perioperative outcomes after minimally invasive esophagectomy.

METHODS

This study was a single-institution retrospective review of patients undergoing minimally invasive esophagectomy for high-grade dysplasia or cancer of the esophagus between 1999 and 2004. A body mass index of 30 or greater was considered obese. Patients with a body mass index less than 18.5 were excluded because of the potentially adverse effects of malnutrition on outcomes.

RESULTS

A total of 282 eligible patients were identified. There were 84 obese and 198 nonobese patients (mean body mass index = 34.5 versus 25.5; p < 0.0001). Preoperative demographics, comorbidities, and cancer status were similar, except for a higher prevalence of diabetes (p = 0.002), lower prevalence of peripheral vascular disease (p = 0.045), and lower prevalence of stage III disease in the obese group (p = 0.044). Operative time was significantly longer in obese patients (375 versus 301 minutes; p = 0.0001), and estimated blood loss was similar (433 versus 377 mL, obese versus nonobese, respectively). There were 5 (1.8%) overall 30-day perioperative mortalities, with no differences between the groups. Overall major (obese, 23 [27.5%] versus nonobese, 68 [34.3%]) and minor (obese, 23 [27.5%] versus nonobese, 65 [32.8%]) complication rates were also similar. Furthermore, there were no significant differences in any individual complications. There was no difference in median intensive care unit stay (obese, 1 day versus nonobese, 2 days) or overall hospital stay (obese, 7 days versus nonobese, 8 days).

CONCLUSIONS

Obesity was associated with longer operative times. Our review suggests that obesity is not a risk factor for mortality, postoperative complications, or length of hospitalization after minimally invasive esophagectomy.

Obesity prevalence from a European perspective: a systematic review

Background

Obesity has been recognised as an important contributing factor in the development of various diseases, but comparative data on this condition are limited. We therefore aimed to identify and discuss current epidemiological data on the prevalence of obesity in European countries.

Methods

We identified relevant published studies by means of a MEDLINE search (1990–2008) supplemented by information obtained from regulatory agencies. We only included surveys that used direct measures of weight and height and were representative of each country's overall population.

Results

In Europe, the prevalence of obesity (body mass index ≥ 30 kg/m²) in men ranged from 4.0% to 28.3% and in women from 6.2% to 36.5%. We observed considerable geographic variation, with prevalence rates in Central, Eastern, and Southern Europe being higher than those in Western and Northern Europe.

Conclusion

In Europe, obesity has reached epidemic proportions. The data presented in our review emphasise the need for effective therapeutic and preventive strategies.