The Health Benefits of a Healthy Diet Combined with Physical Exercise
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Specific body composition components seem to be the key in the development of several obesity-associated chronic non-communicable diseases. In particular, excess visceral fat and loss of muscle mass, which occurs with increasing age, have been associated with signs of chronic systemic immune activation (inflammaging), as well as a higher risk for a broad spectrum of health outcomes including cardiovascular disease, type 2 diabetes (T2D), and neurodegenerative diseases, which together make up the current epidemic in non-communicable chronic disease epidemic. Effective strategies targeting specific body composition components beyond weight management may help to improve the health span, e.g. healthy longevity.
“…a review of 18 intervention trials with or without calorie restriction revealed that a MedDiet intervention can significantly reduce measures of central obesity…”
The Mediterranean diet (MedDiet), and particularly a calorie-reduced MedDiet, has emerged as an effective strategy for weight loss and its long-term maintenance. Results of the previous PREDIMED trial that did not introduce any caloric reduction have already shown that a diet with a high proportion of fruits and vegetables and reduced amount of red meat, sugar and highly processed foods is an optimal approach for weight loss, and for the prevention of cardiovascular disease and cognitive decline. In addition, a review of 18 intervention trials with or without calorie restriction revealed that a MedDiet intervention can significantly reduce measures of central obesity, as determined by waist circumference, waist-hip ratio, or visceral fat mass. In addition, there is an established positive effect of physical exercise on visceral fat in adults with overweight, and on muscle mass and function in healthy older adults.
The results published in the journal JAMA Network Open by a group of prominent investigators with first author Jadwiga Konieczna were based on an interim analysis (after 3 years of follow-up) in a subset of participants in the ongoing PREDIMED-Plus randomized controlled trial. The larger trial is being conducted in 23 Spanish research centers and includes a total of 6874 women and men (age 55-75 years) with body mass index between 27 and 40 and metabolic syndrome. Of the 6874 total PREDIMED-Plus participants, a subsample of 1521 individuals, coming from centers with access to a technique to assess body composition measurements (DXA) at 3 time points.
“[The PREDIMED-Plus study aimed] …to assess the effects of a lifestyle intervention combining a calorie-restricted MedDiet and physical activity on body composition in older individuals.”
The PREDIMED-Plus study is a parallel-group, single-blinded trial aimed to assess the effects of a lifestyle intervention combining a calorie-restricted MedDiet and physical activity on body composition in older individuals. The two primary endpoints of the study were: (1) the incidence of cardiovascular disease (a composite of nonfatal myocardial infarction, nonfatal stroke, and cardiovascular death), and (2) weight loss and its long-term maintenance. Secondary endpoints were waist circumference, type 2 diabetes (T2D), and mortality)
Participants in the intervention group received a tailored face-to-face nutritional and behavioral program. In addition to 30% calorie reduction, they were encouraged to limit consumption of certain foods common in the Standard American diet (processed meats, butter, margarine, cream, sweetened beverages, added sugar, biscuits, and bread and other refined cereals) while consumption of whole grains were encouraged.
Participants were also encouraged to progressively increase aerobic physical exercise, with the final goal of walking 45 minutes per day or more or the equivalent during 6 days per week, and doing exercises to improve strength, flexibility, and balance. Participants from the intervention group were contacted by trained dietitians 3 times a month during the first year. They also received behavioral and motivational support strategies including self-monitoring, goal setting, and problem solving.
“…a multifactorial lifestyle intervention (education, diet and physical exercise) was effective in reducing total body fat and visceral fat, in addition to attenuating age-related decreases in lean body mass.”
Results from this interim analysis of an ongoing primary prevention trial indicate that a 3-year weight loss intervention based on a calorie-reduced MedDiet, and regular physical activity resulted in moderate but significant improvements in body composition in middle-aged and older adults with increased body weight and metabolic syndrome. In particular, the results showed that a multifactorial lifestyle intervention (education, diet and physical exercise) was effective in reducing total body fat and visceral fat, in addition to attenuating age-related decreases in lean body mass.
Based on their findings, the authors suggest that lifestyle interventions for weight loss should include strategies such as regular physical exercise preserving lean body mass to delay age-dependent loss of muscle mass or sarcopenia (loss of muscle mass and strength.
What is the take home message of this impressive research study?
On the one side, the benefits of this intervention were relatively small, and the study design does not answer the question if a sustained 30% calorie restriction alone would have resulted in similar benefits. Similarly, it may have been easier in this Spanish population to promote a Mediterranean diet, than in countries where such a diet is not consumed by the majority of people, like the US. Also the behavioral counseling to keep people motivated to exercise daily and restrict their caloric intake by 30% is not available for the majority of people.
“…switching to a healthy dietary pattern alone may not be sufficient to reduce visceral fat and maintain muscle mass.”
On the positive side, it is one of the few well controlled lifestyle intervention studies that allows us to make conclusions about the causal role of such an intervention. The majority of epidemiological studies in this field are of a correlational nature, e.g. they don’t prove causality. The study results are important as they demonstrate that switching to a healthy dietary pattern alone may not be sufficient to reduce visceral fat and maintain muscle mass as seen with this multifactorial intervention.
The best way to translate these important insights into population-based increases in healthy longevity requires public education and a major shift in our disease care system (based on prescribing expensive medications like Wegovy for obesity and associated chronic diseases) to a true healthcare system focusing on the promotion and public acceptance of relatively simple lifestyle changes.