New Clues to Prevent Weight Regain

Hunter, G.R., et al. 2015. Exercise training and energy expenditure following weight loss. Medicine
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Science in Sports
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Exercise, 47 (9), 1950–57.

Introduction

Cardiovascular exercise and resistance training are essential to successful weight management. However, there is a complex, unclear relationship between exercise training during weight loss and free-living energy expenditure after weight loss (Hunter et al. 2015).

Some earlier studies have suggested that people move less after weight loss, while others have found no change. This unsolved mystery motivated Hunter and fellow researchers to investigate the effects of (1) aerobic exercise, (2) resistance training and (3) no exercise during a low-calorie weight loss program, and to determine the impact of each on activity-related energy expenditure and nonexercise activity thermogenesis (NEAT, often called spontaneous movement).

Study Methods

The study’s 140 volunteers were overweight women aged 20–44; none had exercised for a year and each had a body mass index between 27 and 30. After a 4-week weight stabilization period (with daily meals provided in weeks 3 and 4), the women were divided into three groups:

• aerobic-and-diet training: weight loss with aerobic exercise three times per week
• resistance-and-diet training: weight loss with resistance exercise three times per week
• control: weight loss with no exercise training

All the women received an 800-kilocalorie-per-day diet until their BMI fell below 25, which took approximately 16 weeks for all 3 groups. The furnished diet’s macronutrient breakdown was 20%–22% fat, 20%–22% protein and 56%–58% carbohydrate.

Aerobic Training

The aerobic training group did supervised indoor walking and/or jogging, starting at 67% of maximum heart rate (MHR) for 20 minutes. MHR was determined from a graded maximal aerobic capacity exercise test. Cardiovascular duration and intensity training increased gradually week by week. By the 8th week of training, the women were doing 40 minutes of aerobic exercise at 80% of their MHR, and they maintained this level for the rest of the 16-week study.

Resistance Training

The resistance training group completed a 1-week familiarization of all of the exercises, which included leg extension, leg curl, squat, biceps curl, triceps extension, latissimus dorsi pull-down, bench press, military press, low-back extension and bent-leg sit-up.

All the women then completed 1-repetition-maximum (1-RM) testing to determine the appropriate percent of lifting capacity for each major exercise group. They began with 1 set of 10 repetitions at 65% of their 1-RM, increasing gradually each week until they were training at 80% of their 1-RM. On week 5, they began completing 2 sets of 10 repetitions at 80% of their 1-RM (which they maintained for the rest of the study), resting 2 minutes between sets. Muscular strength was reevaluated every 5 weeks, and loads were adjusted to sustain the 80% of 1-RM exercise intensity for major exercises.

No Exercise

The no-exercise group served as the control for this study. Participants consumed an 800-kcal-per-day diet and did no exercise.

Results and Discussion

All the women in this 16-week study lost an average of 25 pounds. Total daily energy expenditure decreased by 63 kcal per day in the aerobic-and-diet training group and fell by 259 kcal per day in the no-exercise group. The resistance-and-diet training group increased total daily energy expenditure by 63 kcal per day.

Activity-related energy expenditure increased by 13 kcal per day and 109 kcal per day for the aerobic training and resistance training groups, respectively. In the no-exercise group, activity-related energy expenditure decreased by 142 kcal per day (thus showing that people start to move less during low-kilocalorie interventions). With NEAT, the aerobic training group showed a decrease of 87 kcal per day, while the resistance training group had an increase of 61 kcal per day. The no-exercise group had a decrease of 143 kcal per day for NEAT. The dramatic drop in total daily energy expenditure in the no-exercise group, as contrasted with the aerobic-and-diet and resistance-and-diet training groups (see Table 1), is very meaningful information for personal trainers to share with clients.

Hunter et al. 2015 remark that exercise training, particularly resistance training, increases daily energy expenditure by increasing muscle mass (muscle is very metabolically active tissue). In addition, they explain that postexercise oxygen consumption (EPOC) contributes to the body’s total daily energy expenditure.

NEAT (nonexercise movement) interventions can be a primary strategy for helping people avoid weight gain after a weight loss intervention, say Hunter and colleagues. The importance of NEAT for metabolic health is further discussed in the sidebars. Personal trainers clearly need to persuade clients that moving more during the day will help them lose weight, prevent weight regain and sustain their metabolic health.

The percentage of fat loss in this 16-week intervention was 10.1% for the aerobic-and-diet training group, 10.6% for the resistance-and-diet training group and 9.2% for the no-exercise group. This shows that exercise promotes fat loss during a very low-calorie intervention (800 kcal per day).

Final Thoughts

The results of this study clearly show that exercise training is critical for maintaining NEAT and activity-related energy expenditure after weight loss, and thus they confirm what many personal trainers know from experience—that people who go on diet-only interventions are quite susceptible to weight regain following the diet.

The study also shows that resistance training is particularly important in a dietary weight loss intervention, as this type of exercise appears to do the most good in preventing weight regain.