Prevalence of obesity has achieved massive proportions in several countries [1]. Even parts of the world with a low absolute prevalence of overweight/obesity are now showing spectacular increases leading to a rapid rise in the prevalence of chronic metabolic diseases such as type 2 diabetes [2]. Obviously, to reduce the adiposity of high-risk obese patients, the laws of thermodynamics dictate that we recommend a hopefully manageable and tolerable negative energy balance resulting from a combination of reduced caloric intake and increased energy expenditure through more physical activity/exercise. Thus, in principle, fixing the obesity epidemics should be easy: patients should eat less and be more physically active and they should exercise more.
The medical field has encountered difficulties in properly conveying this message to overweight/obese patients. For instance, considerable focus has been placed on calorie counting and on reducing dietary fat intake. As a consequence, the “low-fat” diet recommendations have led patients to consume more carbohydrates. As counting calories is rather tedious and technically demanding, most patients are not successful in reducing their caloric intake on the long term and the low-fat/high-sugar diet has contributed to generate a large contingent of patients who are abdominally obese, insulin resistant and with the high triglyceride/low HDL cholesterol dyslipidemia. Accordingly, the prevalence of type 2 diabetes has achieved historical heights worldwide [2].
Thus, which lifestyle messages should be conveyed to the population in order to prevent weight gain remains an issue with considerable clinical/public health implications. In this regard, the paper recently published in the New England Journal of Medicine by Mozaffarian and colleagues [3] from the Department of Epidemiology and Nutrition at Harvard University provides important information regarding the key elements of our lifestyle promoting weight gain over time.
In this landmark paper, the authors analyzed three distinct cohorts that included 120 thousand U.S. women and men free of chronic disease and not obese at baseline [3]. These cohorts were the Nurses’ Health Study (NHS), the Nurses’ Health Study II (NHS II) and the Health Professionals Follow-up Study (HPFS). Participants of these three studies were followed with biennial validated questionnaires on their medical history and lifestyle habits. After exclusion of participants with co-morbidities or missing data at baseline, all individuals below 65 years of age were analyzed including 50,422 women in the NHS, 47,898 women in NHS II and 22,557 men in HPFS. The relationships between changes in various lifestyle factors and changes in body weight were assessed at 4-year intervals. As cohort specific and sex-specific results were remarkably similar, they were combined for a pooled analysis.
Subjects gained an average of 3.35 lbs at every 4-year period. When the authors examined the relationship of weight changes with daily servings of individual dietary components, they found that 4-year changes in body weight were associated with servings of potato chips, potatoes (particularly French fries), sugar-sweetened beverages and unprocessed and processed meats and inversely related to intake of vegetables, whole grains, fruits, nuts and yogourt. Physical activity was another factor which was associated with less weight gain over the follow-up periods. The investigators also found that alcohol, stopping smoking, lack of or excess sleep and television watching were all factors associated with weight gain over time. Another important observation that the authors made was that although each of these factors had a modest impact on body weight gain over time, aggregate dietary changes were associated with considerable weight gain with time.
Thus, this study provides critically important information to guide our patients. Taken globally, there are several important but simple metrics of diet quality which could be used in our recommendations. For instance, rather than imposing to our patients the onerous task of counting calories and monitoring their fat intake, limiting the intake of potato chips, French fries, sugar-sweetened beverages, meat, encouraging the intake of fruits, vegetables, whole grains, nuts and yogourt and promoting regular physical activity, and enough sleep while limiting television watching should result, in patients compliant to these recommendations, in better weight control and maybe weight loss over time. It is important to keep in mind that rather small changes in daily energy balance (even 50-100 kcal/day) could result in considerable weight loss if successfully maintained over years.
Thus, as suggested by the authors, clinical and public health strategies to limit the consumption of calories would probably be more effective if we could move from a technical discussion about the macronutrient composition of the diet to a focus on specific foods and beverages which are simple metrics of diet quality while also focusing on physical activity, sedentary time, and quality of sleep.
References
- Finucane MM, Stevens GA, Cowan MJ, et al. National, regional, and global trends in body-mass index since 1980: systematic analysis of health examination surveys and epidemiological studies with 960 country-years and 9.1 million participants. Lancet 2011; 377: 557-67. PubMed ID: 21295846
- Danaei G, Finucane MM, Lu Y, et al. National, regional, and global trends in fasting plasma glucose and diabetes prevalence since 1980: systematic analysis of health examination surveys and epidemiological studies with 370 country-years and 2.7 million participants. Lancet. 2011; 2;378: 31-40. PubMed ID: 21705069
- Mozaffarian D, Hao T, Rimm EB, et al. Changes in diet and lifestyle and long-term weight gain in women and men. N Engl J Med 2011; 364: 2392-404. PubMed ID: 21696306