The best lifestyle changes in retirement for fat loss and muscle maintenance Original paper

In this network meta-analysis, calorie restriction alongside any kind of exercise and/or high-protein intake was the most effective method for improving body composition in people of retirement age.

The most effective nutrition and exercise interventions for the improvement of body composition (muscle mass and fat mass), BMI, and waist circumference (WC).

4,957 people with overweight or obesity near retirement age (55–70 years).

Researchers completed a network meta-analysis of 66 randomized controlled trials (RCTs). Each outcome was evaluated alone and then combined in a model according to the following prioritization: relative fat mass, absolute fat mass, lean mass/fat-free mass (markers of muscle mass), WC, and BMI.

Studies were conducted in 19 different countries, but most were conducted in the U.S. Half of the studies included men and women, while most of the remaining studies (27 of 32 studies) only included women. Sample sizes ranged from 16 to 543 participants and intervention durations ranged from 8 to 26 weeks.

Half of the included studies combined nutrition and exercise interventions, while the other half included either nutrition or exercise-focused interventions. Most of the exercise interventions involved training sessions 3 times a week for 20–60 minutes per session. Common exercise modalities were resistance exercise, aerobic exercise, and mixed exercise (a combination of resistance and aerobic exercise). Common nutrition interventions included energy restriction (caloric deficit of 500–1,000 calories per day) and a high protein intake (1.1–1.7 g/kg of body weight per day)

Body composition was mostly measured with dual energy x-ray absorptiometry (DXA, sometimes paired with computerized tomography), though several studies used bioelectric impedance and air-displacement plethysmography, and few used skinfold measurements and underwater weighing.

Combined Analysis

When taking all outcomes into account, energy restriction combined with either (i) resistance training, (ii) mixed exercise, or (iii) any exercise program and a high-protein intake were the most effective strategies for improving body composition. This finding was driven almost entirely by changes in body fat.

Body fat

Absolute (47 studies) and relative (37 studies) body fat changes were the most common outcomes. Energy restriction combined with any kind of exercise and/or a high-protein intake appeared most effective for losing absolute and relative body fat (–4.9 kg to –6.86 kg, –3.45% to –3.99%). Energy restriction alone resulted in fat loss (–4.26 kg, –2.69%). Resistance training or mixed exercise alone also led to body fat loss (resistance training: –1.49 kg, –1.74%; mixed exercise: –2.26 kg, –2.33%).

Lean mass

Mixed exercise increased lean mass (48 studies). Some of the other interventions trended toward increasing lean mass (e.g., resistance exercise) or decreasing lean mass (e.g., energy restriction alone), but these findings were not statistically significant.

BMI

Energy restriction alone or in combination with either a high-protein intake, aerobic exercise, or resistance exercise decreased BMI, whereas resistance training either alone or with a high-protein intake, as well as aerobic training alone, did not (38 studies).

Aging is often associated with changes in body composition that can lead to accelerations in disability and decreases in healthspan and lifespan.^[1] Aging is strongly associated with obesity (i.e., excess body fat) and the relationship appears to be bidirectional.^[2][3] This means that not only do people tend to gain body fat as they age, but gaining body fat also seems to accelerate the development of age-related health conditions. Obesity is a major risk factor for chronic disease (e.g., cardiovascular disease, osteoarthritis, cancer)^[4] and is known to accelerate inflammaging (a chronic state of low-level inflammation associated with aging) and worsening of the immune system.^[5]

As people reach 50, not only does fat mass tend to increase, but muscle mass and function also begin to decrease at a faster rate.^[6][7] Although weight may remain stable or even begin to decrease during aging, decreases in muscle mass can lead to disability and increases or changes in distribution of body fat, possibly resulting in greater amounts of visceral fat, which can increase the risk of chronic disease.^[8] This “hidden muscle wasting” is called sarcopenic obesity and it has been shown to affect a large portion of older people.^[9][10]

Muscle loss during aging

Adapted from Janssen, Heymsfield, and Ross, 2000, J Appl Physiol.^[11]

Since people often retire in later life, and retirement is associated with lifestyle changes in lifestyle, this period of life is a great opportunity to develop new lifestyle, diet, and exercise habits that optimize healthspan and lifespan.^[12][13] In a 2021 meta-analysis of lifestyle habits and longevity, regular physical activity (everything from vigorous activity to walking), engagement in leisure activities, sleeping 7–8 hours a night, and having a BMI in the normal or overweight range (i.e., not underweight or obese) were associated with a decreased risk of death.^[14] Although calorie restriction is critical and effective for weight loss and obesity treatment, other aspects of health require attention for sustainable weight loss and longevity, and calorie restriction alone can lead to muscle loss alongside fat loss.^[15][16] To maintain or increase muscle mass, exercise and adequate protein intake are necessary to trigger protein synthesis and ensure adequate recovery.^[17] Moreover, muscle body mass drives energy use and supports weight maintenance.^[18] In a 2016 meta-analysis, adults over 50 who consumed higher-protein diets (at least 1g/kg of body weight per day) maintained more lean mass and lost more fat during weight loss (i.e., calorie restriction) interventions.^[19]

Overall, the literature supports the main findings of the study under review, suggesting that the most effective strategy for losing fat and maintaining or increasing muscle mass to reach optimal body composition for reduced risk of disability and chronic disease in people over 50 years of age is a combination of calorie restriction and exercise, possibly alongside a high-protein diet.

Adherence was not mentioned in half of the included studies and many studies had an unclear risk of bias for several domains. The results did not change much when studies with a high risk of bias were excluded.

Twelve intervention/control categories were used in the network meta-analysis:

• No intervention
• Energy restriction (i.e., caloric restriction of 500 to 1,000 kcal)
• Energy restriction plus high protein intake (1.1–1.7 g/kg body weight/day)
• Intermittent fasting (5:2 diet)
• Mixed exercise (aerobic and resistance training)
• Resistance training
• Aerobic training
• High-protein intake plus resistance training
• Energy restriction plus high-protein intake plus exercise
• Energy restriction plus resistance training
• Energy restriction plus aerobic training
• Energy restriction plus mixed exercises (aerobic and resistance training combined)

Several studies from the systematic review (26 of the initially included 92 studies) could not be included in the network meta-analysis because of large differences in intervention design that made them difficult to compare to those that fit the meta-analysis criteria.