The researchers used DEXA to determine body composition, including fat free mass and fat mass. Additionally, the resting metabolic rate was measured via indirect calorimetry at the same time intervals outlined above. Researchers then used the doubly labeled water method to determine the average carbon dioxide production rate. Collections were taken for seven days during the competition and fourteen days at the six-year follow-up. Using the rCO2 determined from the doubly labeled water method, the TEE was calculated for everyone. Since energy intake was stable at the pre-competition baseline and the six-year follow-up, TEE was assumed to be the energy intake. During the competition, though, energy intake was estimated by the intake balance method. The average rate of body energy stores was calculated using the fat mass and fat free mass change from baseline at six weeks and at thirty weeks. Additionally, the average TEE for the thirty-week period was the average of the TEE at six weeks into the competition and at thirty weeks into the competition. The average used for the first six weeks was the TEE measurement obtained at the six-week point. Because this may not be representative of the TEE for the whole period, energy intake estimates may be uncertain. Lastly, the physical activity expenditure was calculated as the total energy expenditure (TEE) minus the resting energy expenditure (REE). From that result, the estimated thermic effect of food was subtracted. Physical activity estimates were divided by the body weight of the individual as most physical activity requires movement of the body.
The results showed that the median weight loss was 13%. The seven contestants above the mean averaged a loss of 24.9% ± 3.8% and the seven below the median threshold averaged 1.1% ± 4%. While energy intake had a significant correlation during the weight change at weeks six and thirty during the competition, there was not a significant correlation at thirty years among both groups. Adversely, there was a significant correlation at the six-year follow-up with physical activity, as those who fell into the above median loss group had much higher physical activity than those individuals who fell below the median loss of 13%. The was a significant correlation between absolute energy intake and physical activity and weight loss at six years, but there was not a significant correlation between weight regain and energy intake at the six-year follow-up. Physical activity was significantly correlated, though. During the show, the six- and thirty-week measurements demonstrated significant correlation to energy intake and weight loss, though.
There hasn’t been a lot of research over longer time periods on extreme weight loss. This study was able to do so using the gold standard doubly labeled water method to measure both energy intake and physical activity beyond just the first year of weight loss. In future studies, it may be beneficial to check in with contestants each year, as opposed to waiting six years. Though this study included males and females, differences and comparisons were not included. It would be interesting to know among the two groups – those who fell above the weight loss median and those who fell below, if there was a normal distribution of males and females in each group or if there were significant changes between the two genders at each measurement point. Moreover, it would also be interesting to compare racial and ethnic groups and differences or comparisons that could be drawn. The researchers also noted that their use of TEE measurements for energy intake during the competition could have been done differently to be more accurate. The TEE taken at the six week point of the competition was used as the average for the first six weeks of the competition. For the 30 weeks, the average of the six week and thirty-week data was used. This measurement could have been taken more frequently to increase the accuracy of TEE.
Overall, this article was informative about the long-term effects of extreme weight loss on a relatively small sample size. This study is a great steppingstone for future research to build upon. On top of additional information related to gender, age and ethnicity, more specific information on the weight loss amounts for each participant may be helpful to dive further into. For example, is more physical activity likely required to maintain weight loss in an individual who lost one hundred pounds versus an individual who lost fifty pounds at the six-year follow-up point and do the physical activity requirements for maintenance increase slowly over time? It would also be helpful if those findings were then compared to a control group who has maintained a healthy weight for the same period to fully understand the impact of extreme weight gain and weight loss.
Kerns, J. C., Guo, J., Fotherfill, E., Howard, L., D., K. N., Robert, B., . . . Hall, K. D. (2017). Increased Physical Activity Associated with Less Weight Regain Six Years After “The Biggest Loser” Competition. OBESITY BIOLOGY AND INTEGRATED PHYSIOLOGY, 1838-1843.