Based on body mass index (BMI), more than 70% of American adults are classified as overweight or obese.6  Unfortunately, this height and weight calculation seriously underestimates the number of middle-aged and older adults who have too much fat and too little muscle.  This is due to the fact that men and women who do not perform regular resistance exercise lose between 5 and 10 pounds of lean (muscle) weight each decade of life.7,16  Consequently, a non-strength training individual who weighs the same at age 60 as at age 20 has at least 20 pounds less muscle and 20 pounds more fat, even though the BMI number is exactly the same.  Muscle loss results in resting metabolic rate reduction of 2 to 4 percent per decade.5,10,14,17  Because resting metabolism is responsible for more than 60 percent of daily energy expenditure in inactive adults,9  metabolic slow down leads to fat gain.21,26

The most prevalent approach to fat gain is a low-calorie diet plan.  According to the American Medical Association,20  70 percent of American adults are eating reduced calorie diets in order to attain a more desirable body weight.  Although dieting is a productive means for temporarily reducing body weight, it is essentially ineffective for maintaining the lower body weight.4,15  Research clearly demonstrates that almost all successful dieters regain the weight they lost within a relatively short period of time. 4,15   This undesirable outcome is largely due to the muscle loss and metabolic rate reduction that occurs during periods of calorie restriction.11  In fact, research reveals that approximately 25 percent of the weight lost through dieting is muscle tissue.1,8,19,23  Dieting, therefore, exacerbates two of the major factors responsible for fat gain in the first place, namely muscle loss and metabolic rate reduction.

With this in mind, it makes sense to couple a sensible diet plan, (effective for losing fat),4,15 with a reasonable program of resistance exercise (effective for increasing muscle and metabolism).3,12,18  Although it might seem logical to combine dieting with aerobic activity, research indicates that this actually increases muscle loss.2,22  A 2017 weight loss study by Beavers et al.2  compared the body composition effects of diet alone, diet with aerobic activity, and diet with resistance exercise over a 6-month intervention period.   The diet only group lost 11.2 pounds of fat weight and 2.4 pounds of lean (muscle) weight.  The diet with aerobic activity group lost 14.1 pounds of fat weight and 3.3 pounds of lean weight.  The diet with resistance exercise group experienced the most fat weight loss (-17.2 pounds) and the least lean weight loss (-1.5 pounds).

Another 2017 weight loss study found that the body composition changes attained by dieting with aerobic activity could be improved upon by adding resistance exercise.22   After 6 months, the diet with aerobic activity group lost 13.9 pounds of fat weight and 5.9 pounds of lean (muscle) weight, whereas the diet with aerobic activity and resistance exercise group lost 15.4 pounds of fat weight and 3.7 pounds of lean weight.  Of course, any lean weight loss is undesirable, as this negatively impacts health, fitness, function, metabolism, and appearance.

In an attempt to concurrently decrease fat weight and increase lean (muscle) weight, we recently conducted a 6-month weight loss study.25   To avoid excessive caloric deficit, our research participants followed a moderate diet plan in which the men consumed 1,500 – 1,800 daily calories and the women consumed 1,200 – 1,500 daily calories.  To avoid detrimental protein reduction, our study subjects consumed 2 daily meal replacement protein shakes (each providing about 24 grams protein and 36 grams carbohydrate).  To avoid excessive energy utilization, our research participants performed a 40-minute workout (20 minutes of aerobic activity interspersed with 20 minutes of resistance exercise), 2-3 days per week.  This basic and practical intervention program resulted in 14.1 pounds less fat weight and 3.7 pounds more lean weight.  Our subjects actually improved their body composition by 17.8 pounds, with concurrent fat loss and muscle gain.  This unusual but desirable study outcome reverses the fat gain and muscle loss associated with aging, thereby enhancing health and fitness, as well as reducing the risk of weight regain.  It would appear that a weight loss program consisting of moderate caloric restriction, increased protein intake, and combined aerobic/resistance exercise is effective for both reducing body weight and improving body composition.  Additionally, our program participants attained significant reductions in waist girth, hip girth, resting blood pressure, and blood sugar (HbA1c).25

However, these impressive 6-month results are only as good as their sustainability after discontinuation of the diet plan.  With relatively rare exceptions, almost all successful weight loss programs are followed by a return to pre-diet body weight after resuming normal caloric consumption.4,15   Therefore,  we conducted a follow-up weight maintenance study in which our prior weight loss study participants eliminated caloric restriction, switched from 2 daily meal replacement protein shakes to 1 daily meal replacement protein shake, and continued the same basic exercise program (40 minutes, 2-3 days per week).24   After 9 months without caloric restriction, our weight maintenance program participants had the same body weight and a significantly better body composition.  Although they did not regain any body weight, they continued to reduce fat and rebuild muscle throughout the 9-month post-diet period.  This is one of very few weight maintenance studies to actually avoid weight regain, and the only weight maintenance study to attain continued body composition improvement with concurrent fat loss and muscle gain.


A major reason for the epidemic of overweight and obesity is aging-associated muscle loss and metabolic rate reduction, which typically leads to fat accumulation.7,14,21,26   Diet only programs and diet plus aerobic activity programs result in both fat loss and muscle loss, thereby exacerbating the underlying problem and making it most difficult to avoid weight regain. 1,2,8,22 Performing resistance exercise during dieting is effective for reducing muscle loss.2,22  However, performing resistance exercise and increasing protein intake during dieting is a more desirable intervention, as this approach enables weight loss with concurrent fat loss and muscle gain.13,25

Key factors for successful weight loss and body composition improvement appear to be:

  • Reduced but reasonable caloric consumption, such as 1,200 – 1,500 calories/day for women, and 1,500 – 1,800 calories/day for men).
  • Increased protein intake, such as 2 daily meal replacement protein shakes.
  • Basic and brief exercise program, such as 2-3 weekly workouts featuring 20 minutes of aerobic activity and 20 minutes of strength training.

Key factors for successful weight maintenance and continued body composition improvement appear to be:

(1) Increased protein intake, such as 1 daily meal replacement protein shake.

(2) Basic and brief exercise program, such as 2-3 weekly workouts featuring 20 minutes

of aerobic activity and 20 minutes of strength training.

Our results support a simple, sensible, and practical approach to attaining and maintaining a healthy body weight and body composition.   Additionally, unlike most weight loss and weight maintenance programs that have a relatively low completion percentage, our program of moderate food intake, satisfying meal replacement shakes, and manageable exercise frequency/duration elicited a high level of participant compliance.  The subject completion rate in our 6-month weight loss study was 83 percent,25   and the subject completion rate in our 9-month weight maintenance study was 82 percent.24     

Note.  With respect to the nutrition program, participants who did not like to drink protein shakes were allowed to substitute protein bars with similar amounts of protein (20 grams) and carbohydrate (32 grams).  Also, to ensure appropriate intake of vitamins and minerals, participants took a daily vitamin/mineral complex that included 500 mg of calcium and 1,200 IU of vitamin D.  All of the nutritional products were provided by Shaklee Corporation (Pleasanton, CA).

Wayne WL and La Rosa Loud R. Addressing The Obesity Epidemic. AHHF GAMUT, Issue, 62, July/Aug 2018.

Wayne L. Westcott, Ph. D., is Professor and Director of Exercise Science at Quincy College in Quincy, MA, and author of 28 strength training books.  Rita La Rosa Loud, B.S., is Director of the Health & Fitness Research Center at Quincy College. 

Updated 03 August 2018


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