Obesity and being overweight are associated with chronic medical conditions caused or worsened by metabolic dysfunction. This has given rise to multiple targeted interventions centered around lifestyle modifications and dietary changes.

To date, little is known about how these interventions impact body composition. A new study in JAMA Network Open examines this aspect of non-pharmaceutical weight control interventions.

Study: An energy-reduced Mediterranean diet, physical activity, and body composition: an interim subgroup analysis of the PREDIMED-Plus randomized clinical trial. Image Credit: Antonina Vlasova / Shutterstock.com

About the study

The Mediterranean diet (MedDiet) has been established as one of the healthiest diets in terms of weight management and cardiovascular health, with or without energy reduction. Moreover, the MedDiet is associated with a smaller waistline, reduced visceral fat storage, and lower waist-hip ratio.

However, the effects of the MedDiet in association with increased physical activity on body composition measurements have not yet been reported. The current study is an interim analysis of data from an ongoing randomized clinical trial (RCT) called the Prevención con Dieta Mediterránea-Plus (PREDIMED-Plus) that aims to explore the effects of these coupled lifestyle modifications on cardiovascular disease rates eight years from the intervention.

The PREDIMED-Plus trial is being conducted over 23 centers in obese women and men at least 55 years of age. All study participants have a body mass index (BMI) between 27-40 km/m² and exhibit signs of metabolic syndrome.

Dual energy X-ray absorptiometry (DEXA) measurements of body composition were obtained from about 1,500 individuals.

What did the study show?

Study participants were randomly assigned to either an intervention group, which involved a customized 30% energy-reduced Mediterranean diet (MedDiet) in addition to physical activity, or the control group, which was advised to follow the MedDiet without specific guidelines on physical activity. The changes in total body fat and lean mass, as percentages of the body mass, and visceral fat were measured at three years.

The mean age was about 64 years, with men account for 52% of the study cohort. In the intervention group, the mean total fat mass was reduced by 1.1% at one year as compared to baseline readings and 0.96% at three years.

Visceral fat reduced by 154 grams and 116 grams at one and three years, respectively, in the intervention group. Total lean mass increased by 1% and 0.5% at these time points, respectively.

In contrast, these measurements were unchanged in the control group. Thus, when comparing the intervention to the control group, there were significant differences in the magnitude of change in all outcomes.

In the intervention group, individuals lost a mean of about 1.7 kg of total fat at one year; however, these individuals subsequently rebounded, which led to a net loss of one kg at three years.

Intervention participants lost 300 grams of lean mass at one year and about 630 grams at three years, which reflects a slowing in age-related lean mass loss. The lean to fat mass ratio rose with time in the intervention group but not the control group.

There were small improvements in the fat distribution profile, with less visceral fat as a percentage of total fat and android to gynoid fat in the intervention group. No significant differences were observed in the control group.

Those in the intervention group exhibited a greater reduction in percentage total fat by 0.9% at one year and 0.4% at three years as compared to the control group. Visceral fat was reduced by an additional 126 grams and 70 grams at one and three years, respectively.

The lean mass percentage increased by an additional 0.9% at one year and 0.34% at three years in the intervention and control groups, respectively.

Overall, the intervention group was more likely to have an improved body composition by at least 5% as compared to the controls. The risk for total fat mass was reduced by 13% at one year and 6% at three years.

For lean mass, the risk reduction at one and three years was 11% and 6%, respectively. In terms of visceral fat mass, the corresponding improvements were 14% and 8%, respectively.

For every 12 individuals to whom the intervention was applied, there was at least one person who exhibited potentially significant improvements in visceral fat mass. Comparatively, one in every 17 individuals exhibited significant improvements in lean mass in the intervention group.

Adults younger than 65 years experienced more rapid but less stable improvements as compared to older adults. All measurements significantly changed in non-diabetic patients.

What are the implications?

The energy-reduced MedDiet coupled with physical activity may help achieve a clinically improved body composition, with lower total and visceral fat along with higher lean or muscle mass with increasing age, in non-diabetic older adults with a high BMI and metabolic syndrome.

It appears that visceral mass is lost only with the loss of more total fat mass over time in this population of older adults. Moreover, with this regimen, lean mass loss was restricted, which led to an overall increase in the proportion of lean mass to total body mass.

Participants in the intervention group achieved weight loss preferentially at the expense of total fat rather than lean mass.”

Lean mass should be preserved during all weight management interventions, as its loss may aggravate aging-related muscle mass loss or sarcopenia. Lean mass also promotes energy expenditure by muscle tissue, thereby delaying or preventing the regaining of lost weight.

Follow-up of these study participants is ongoing to monitor the clinical relevance of these promising changes in terms of the long-term impact on cardiovascular disease incidence and events.