Changes in Fitness following a Behavioral Weight Loss Program in Severely Obese Individuals

Abstract

Behavioral weight loss programs that include both dietary and exercise components typically result in fitness improvements. However, severely obese individuals (BMI≥40 kg/m2) are often excluded from these programs; therefore it is unclear whether this population achieves similar increases in fitness and who among them are most likely to experience the greatest improvements. PURPOSE: To examine the effect of an intensive lifestyle intervention (ILI) on fitness and to identify factors associated with changes in fitness following a 1- year weight loss intervention. METHODS: 2570 participants in the Look AHEAD trial for individuals with type 2 diabetes were randomized to ILI and 2575 were randomized to the diabetes support and education (DSE) arm. ILI participants were instructed to reduce their caloric intake and increase their exercise to ≥175 min/week while DSE participants received general weight loss guidelines. All subjects completed a maximal exercise test at baseline and a submaximal test to 80% of age-predicted maximal heart rate (HRmax) at 1-year. Change in fitness was calculated as the difference in the MET value at 80% HRmax between baseline and 1-year. RESULTS: Severely obese ILI participants (N=492; BMI: mean±sd=44.8 ± 3.9 kg/m2,age: 56.4 ± 6.4 years; 66.2% female) had significant (p<0.001) improvements in absolute fitness (0.98 ± 1.2 METs) and % change in fitness (24.4 ± 30.1%) at 1-year which were significantly greater than individuals in DSE with severe obesity (p<0.001). Among ILI participants, absolute fitness was similar (p=0.68) and % change in fitness (p<0.05) was greater among the severely obese compared to those with a BMI <40. In ILI participants who were severely obese, those who had a lower baseline BMI, were younger, less fit, and were male, experienced the greatest improvements in fitness at 1 year (ps<0.001). CONCLUSIONS: Severely obese individuals achieved significant improvements in fitness at 1-year in an intensive lifestyle intervention that were similar to those with lesser degrees of obesity. Severely obese participants who were less fit at baseline experienced the largest improvements in absolute fitness at 1- year, suggesting that these individuals may receive the greatest fitness benefit from a behavioral weight loss program.