Journal Title (Medline/Pubmed accepted abbreviation): Am. J. Clin. Nutr.
Page numbers: 767-774
doi (if applicable): 10.3945/ajcn.110.004895
Summary of background and research design:
Background: Weight loss improves many aspects of health in people who are overweight and obese. However, intentional weight loss often causes a decrease in fat mass (good) and fat free mass (bad, since muscle has a key role in hormone regulation and other body functions). Intentional weight loss is also followed by unintentional weight gain (about 95% of people who lose weight regain it within 5 yrs).
Research question: How does the composition of unintentional weight gain (fat:lean mass) compare to that lost intentionally?
This study is a follow up to a previously published weight loss study (Nicklas et al., Am. J. Clin. Nutr., 2009, 89: 1043-52.) These women were involved in a 5 month diet program with 3 levels of physical activity (none, moderate intensity, or vigorous)
Subjects: In total, 95 originally sedentary post-menopausal women with a BMI of 25-40 kg/m2.
Experimental design: follow up (no intervention)
Protocol : Six and 12 months after the 5 month diet (and exercise in some) intervention, the participants returned to the laboratory for assessment of body composition. They were assessed for weight and waist and hip circumference. Also, whole body fat mass, lean mass, and body fat percentage were examined by dual-energy x-ray absorptiometry (DEXA). These values were compared to those obtained both before and after the intervention.
Summary of research findings:
- From the intervention study, women lost 12.1 ± 4.5 kg (13.4 ± 4.6% of initial body weight). Both fat mass and fat free mass decreased significantly and the decreases were not different between intervention groups for each.
- Regain of weight did not vary between intervention groups.
- There was large variation in the quantity of mass that was regained during the 12 mos post-intervention. Unfortunately, 84% of the participants regained more than 2 kg during the 12 mo post-intervention period. However, on average, the participants remained 9% lighter than pre-intervention. Sixteen percent of the women weighed more after 12 mos than pre-intervention.
- Amount of lean body mass did not change during the post-intervention period so, at 12 mo, it was still lower than at baseline.
- In those who did not gain more than 2 kg in the 12 mo post-intervention: They experienced a healthful net increase in their lean mass:fat mass ratio.
- For those who gained greater than or equal to 2 kg: Of the weight lost during intervention, 67% was fat and 33% was lean tissue. The weight gained during the 12 mo post-intervention was 81% fat and 19% lean.
- Waist-to-hip ratio decreased on average during the 12 mo follow up period.
Key practice applications:
A large portion of weight that was lost during the intervention period was regained by most of the women in this study during the 12 mo after intervention. The weight that was regained had proportionally more fat than the weight that was lost. This emphasizes that healthy dietary habits and exercise routines should become part of one’s lifestyle in order to maintain a healthy body composition after weight loss.
There was not a control group that did not partake in the intervention, so it is unknown if these women would have had a healthier body composition if they did not undergo intervention. Also, it would be interesting if these women were followed for a longer time period to see if more subjects regain the weight that was lost and how their body composition continues to change. Lastly, these subjects were postmenopausal women so it may not be appropriate to translate these results to other populations.