Mark A. Pereira

Fast-food habits, weight gain, and insulin resistance (the CARDIA study): 15-year prospective analysis

BACKGROUND Fast-food consumption has increased greatly in the USA during the past three decades. However, the effect of fast food on risk of obesity and type 2 diabetes has received little attention. We aimed to investigate the association between reported fast-food habits and changes in bodyweight and insulin resistance over a 15-year period in the USA. METHODS Participants for the CARDIA study included 3031 young (age 18-30 years in 1985-86) black and white adults who were followed up with repeated dietary assessment. We used multiple linear regression models to investigate the association of frequency of fast-food restaurant visits (fast-food frequency) at baseline and follow-up with 15-year changes in bodyweight and the homoeostasis model (HOMA) for insulin resistance. FINDINGS Fast-food frequency was lowest for white women (about 1.3 times per week) compared with the other ethnic-sex groups (about twice a week). After adjustment for lifestyle factors, baseline fast-food frequency was directly associated with changes in bodyweight in both black (p=0.0050) and white people (p=0.0013). Change in fast-food frequency over 15 years was directly associated with changes in bodyweight in white individuals (p<0.0001), with a weaker association recorded in black people (p=0.1004). Changes were also directly associated with insulin resistance in both ethnic groups (p=0.0015 in black people, p<0.0001 in white people). By comparison with the average 15-year weight gain in participants with infrequent (less than once a week) fast-food restaurant use at baseline and follow-up (n=203), those with frequent (more than twice a week) visits to fast-food restaurants at baseline and follow-up (n=87) gained an extra 4.5 kg of bodyweight (p=0.0054) and had a two-fold greater increase in insulin resistance (p=0.0083). INTERPRETATION Fast-food consumption has strong positive associations with weight gain and insulin resistance, suggesting that fast food increases the risk of obesity and type 2 diabetes.

Major types of dietary fat and risk of coronary heart disease: a pooled analysis of 11 cohort studies

BACKGROUND Saturated fatty acid (SFA) intake increases plasma LDL-cholesterol concentrations; therefore, intake should be reduced to prevent coronary heart disease (CHD). Lower habitual intakes of SFAs, however, require substitution of other macronutrients to maintain energy balance. OBJECTIVE We investigated associations between energy intake from monounsaturated fatty acids (MUFAs), polyunsaturated fatty acids (PUFAs), and carbohydrates and risk of CHD while assessing the potential effect-modifying role of sex and age. Using substitution models, our aim was to clarify whether energy from unsaturated fatty acids or carbohydrates should replace energy from SFAs to prevent CHD. DESIGN This was a follow-up study in which data from 11 American and European cohort studies were pooled. The outcome measure was incident CHD. RESULTS During 4-10 y of follow-up, 5249 coronary events and 2155 coronary deaths occurred among 344,696 persons. For a 5% lower energy intake from SFAs and a concomitant higher energy intake from PUFAs, there was a significant inverse association between PUFAs and risk of coronary events (hazard ratio: 0.87; 95% CI: 0.77, 0.97); the hazard ratio for coronary deaths was 0.74 (95% CI: 0.61, 0.89). For a 5% lower energy intake from SFAs and a concomitant higher energy intake from carbohydrates, there was a modest significant direct association between carbohydrates and coronary events (hazard ratio: 1.07; 95% CI: 1.01, 1.14); the hazard ratio for coronary deaths was 0.96 (95% CI: 0.82, 1.13). MUFA intake was not associated with CHD. No effect modification by sex or age was found. CONCLUSION The associations suggest that replacing SFAs with PUFAs rather than MUFAs or carbohydrates prevents CHD over a wide range of intakes.

Physical activity, falls, and fractures among older adults: a review of the epidemiologic evidence.

OBJECTIVES: Assess the relationship between physical activity and risk for falls and osteoporotic fractures among older adults.

Breakfast Eating and Weight Change in a 5-Year Prospective Analysis of Adolescents: Project EAT (Eating Among Teens)

OBJECTIVE. Breakfast-eating frequency declines through adolescence and has been inversely associated with body weight in cross-sectional studies, with few prospective studies on this topic. This study was conducted to examine the association between breakfast frequency and 5-year body weight change in 2216 adolescents. PATIENTS AND METHODS. Project EAT (Eating Among Teens) was a 5-year longitudinal study of eating patterns and weight concerns among adolescents. Surveys were completed in 1998–1999 (time 1) and 2003–2004 (time 2). Multivariable linear regression was used to examine the association between breakfast frequency and change in BMI, with adjustment for age, socioeconomic status, race, physical activity, time 1 BMI and breakfast category, and time 1 dietary and weight-related variables. RESULTS. At time 1, frequency of breakfast was directly associated with intake of carbohydrate and fiber, socioeconomic status, white race, and physical activity and inversely associated with smoking and alcohol consumption and dieting and weight-control behaviors. In cross-sectional analyses at times 1 and 2, inverse associations between breakfast frequency and BMI remained largely independent of all of the confounding and dietary factors. Weight-related factors (concerns, behaviors, and pressures) explained little of the breakfast-BMI association. In prospective analyses, frequency of breakfast was inversely associated with BMI in a dose-response manner. Further adjustment for confounding and dietary factors did not seem to explain the association, but adjustment for weight-related variables seemed to partly explain this finding. CONCLUSIONS. Although experimental studies are needed to verify whether the association between breakfast and body weight is of a causal nature, our findings support the importance of promoting regular breakfast consumption among adolescents. Future studies should further examine the role of breakfast habits among youth who are particularly concerned about their weight.

DIETARY FIBER AND BODY-WEIGHT REGULATION: Observations and Mechanisms

Dietary fiber may be related to body-weight regulation through plausible physiologic mechanisms that have considerable support in the scientific literature. Many short-term studies suggest that high-fiber foods induce greater satiation and satiety. Epidemiologic studies generally [figure: see text] support a role for fiber in body-weight regulation among free-living individuals consuming self-selected diets, although conclusive intervention studies addressing this point are lacking. Thus, there is considerable reason to conclude that fiber-rich diets, containing non-starchy vegetables, fruits, whole grains, legumes, and nuts, may be effective in the prevention and treatment of obesity in children. Such diets may have additional benefits, independent of changes in adiposity, in the prevention of cardiovascular disease and type 2 diabetes.

Breakfast Frequency and Quality in the Etiology of Adult Obesity and Chronic Diseases

The frequency of eating breakfast has declined over the past several decades, during which time the obesity epidemic has also unfolded. Therefore, there is growing scientific interest in the possible causal role of breakfast in weight control and related disease risks. We conducted a MedLine search for studies that addressed meal frequency, breakfast consumption, and chronic disease risk. Clinical studies document that regular meal consumption can potentially reduce the risk of obesity and chronic disease through mechanisms involved in energy balance and metabolism. Many observational studies have found that breakfast frequency is inversely associated with obesity and chronic disease, but this literature does have some important limitations. Only four relatively small and short-term randomized trials have examined breakfast consumption and body weight or chronic disease risk, with mixed results. Large, long-term, randomized trials are needed.

Influence of leisure time physical activity and television watching on atherosclerosis risk factors in the NHLBI Family Heart Study

Physical activity favorably influences atherosclerosis risk factors but only a few studies in adults considered the time watching television (TV) as a measure of physical inactivity. We therefore determined in a population-based sample of 1778 subjects from the NHLBI Family Heart Study (FHS) whether leisure time physical activity and TV watching have independent or interactive associations with cardiovascular disease risk factors and carotid artery intima-media wall thickness (IMT). Subjects were free from diabetes mellitus and clinically-ascertained coronary artery disease and did not take lipid-lowering or antihypertensive drugs. Only 0.7 and 1.3% of the variance in leisure time physical activity in women and men, respectively, was explained by the amount of TV watching. Leisure time physical activity had a clearly favorable, and TV watching an unfavorable association with anthropometric measurements (BMI (body mass index), waist girth, waist-hip ratio, subscapular and triceps skinfold thickness). The odds ratio (95% CI) of being overweight was 0.41 (0.28-0.62) in women and 0.69 (0.46-1.04) in men in the highest quartile of leisure time physical activity compared to the lowest quartile. The odds ratio increased for increasing quartiles of TV watching to 2.12 (1.45-3.10) in women and 1.61 (1.07-2.43) in men. Watching TV only 1 h per day in women with a BMI of 30 kg/m2 and doing about 75 min of moderate exercise per week was associated with a BMI 1.8 kg/m2 lower than in women watching TV 3 h per day and doing the same amount of exercise. Those with twice the amount of moderate exercise and watching TV 1 h per day had a BMI 0.45 kg/m2 lower. Furthermore, leisure time physical activity was negatively associated with concentrations of triglycerides and positively with HDL cholesterol in both genders. TV watching was significantly positively associated with triglycerides and slightly negatively with HDL cholesterol in men. The observed associations of leisure time physical activity and TV watching with atherosclerosis risk factors were independent from each other. Finally, we analyzed the relation between leisure time physical activity, TV watching and the degree of IMT of the carotid arteries. Neither of these two measures was significantly associated with IMT. In summary, TV watching, in addition to leisure time physical activity, shows an independent association with obesity-related anthropometric measurements, HDL and triglycerides. Decreasing the amount of TV watching might be effective as a first step in reducing atherosclerosis risk factors, especially overweight.

Set points, settling points and some alternative models: Theoretical options to understand how genes and environments combine to regulate body adiposity

The close correspondence between energy intake and expenditure over prolonged time periods, coupled with an apparent protection of the level of body adiposity in the face of perturbations of energy balance, has led to the idea that body fatness is regulated via mechanisms that control intake and energy expenditure. Two models have dominated the discussion of how this regulation might take place. The set point model is rooted in physiology, genetics and molecular biology, and suggests that there is an active feedback mechanism linking adipose tissue (stored energy) to intake and expenditure via a set point, presumably encoded in the brain. This model is consistent with many of the biological aspects of energy balance, but struggles to explain the many significant environmental and social influences on obesity, food intake and physical activity. More importantly, the set point model does not effectively explain the ‘obesity epidemic’ – the large increase in body weight and adiposity of a large proportion of individuals in many countries since the 1980s. An alternative model, called the settling point model, is based on the idea that there is passive feedback between the size of the body stores and aspects of expenditure. This model accommodates many of the social and environmental characteristics of energy balance, but struggles to explain some of the biological and genetic aspects. The shortcomings of these two models reflect their failure to address the gene-by-environment interactions that dominate the regulation of body weight. We discuss two additional models – the general intake model and the dual intervention point model – that address this issue and might offer better ways to understand how body fatness is controlled.

Fiber from Whole Grains, but not Refined Grains, Is Inversely Associated with All-Cause Mortality in Older Women: The Iowa Women’s Health Study

Background: Inconsistencies in epidemiologic findings relating grain fiber to chronic disease may be explained by differentiating nutrient-rich fiber derived from whole grain vs. nutrient-poor fiber derived from refined grain. Objective: Given that phytochemicals are most varied and abundant in the outer layers of grains, we tested the hypothesis that whole grain fiber consumption is associated with a reduced mortality risk in comparison to a similar amount of refined grain fiber. Design: 11040 postmenopausal women enrolled in the Iowa Women’s Health Study, matched on total grain fiber intake, but differing in the proportion of fiber consumed from whole vs. refined grain, were followed from baseline in 1986 through 31 December, 1997, during which time 1341 deaths occurred in 124,823 observed woman-years. Results: After multivariate adjustment in proportional hazards regression, women who consumed on average 1.9 g refined grain fiber/2000 kcal and 4.7 g whole grain fiber/2000 kcal had a 17% lower mortality rate (RR=0.83, 95% CI=0.73–0.94) than women who consumed predominantly refined grain fiber: 4.5 g/2000 kcal, but only 1.3 g whole grain fiber/2000 kcal. Conclusion: Inferences from studies that have reported associations between grain fiber intake and morbidity or mortality may be limited by not differentiating fiber sources. Future studies should distinguish fiber from whole vs. refined grains. Public health policy should differentiate whole grains from refined, and recommend increased consumption of the former.

Soft Drink and Juice Consumption and Risk of Physician-diagnosed Incident Type 2 Diabetes The Singapore Chinese Health Study

Soft drinks and other sweetened beverages may contribute to risk of type 2 diabetes and obesity. However, research has not addressed higher risk and Asian populations. The authors examined the association between soft drinks and juice and the risk of type 2 diabetes among Chinese Singaporeans enrolled in a prospective cohort study of 43,580 participants aged 45-74 years and free of diabetes and other chronic diseases at baseline. The incidence of physician-diagnosed type 2 diabetes was assessed by interview and validated; 2,273 participants developed diabetes during follow-up. After adjustment for potential lifestyle and dietary confounders, participants consuming > or =2 soft drinks per week had a relative risk of type 2 diabetes of 1.42 (95% confidence interval (CI): 1.25, 1.62) compared with those who rarely consumed soft drinks. Similarly, consumption of > or =2 juice beverages per week was associated with an increased risk (relative risk (RR) = 1.29, 95% CI: 1.05, 1.58). The association was modified by 5-year weight gain for > or =2 soft drinks per week among those who gained > or =3 kg (RR = 1.70, 95% CI: 1.34, 2.16) compared with those who gained less weight (RR = 1.20, 95% CI: 1.03, 1.41). Relatively frequent intake of soft drinks and juice is associated with an increased risk for development of type 2 diabetes in Chinese men and women.