Baseline Fitness Decreases Success in Weight Loss Programs

The baseline fitness levels could be a predictor of future success in exercise programs aimed at weight loss.

A team, led by Adnin Zaman, MD, University of Colorado, determined the association between baseline fitness and changes in body weight and device-measured levels of moderate-to-vigorous physical activity (MVPA) during a behavioral weight loss program in data planned for prensation at ENDO 2020, the Endocrine Society’s annual meeting.

Baseline cardiovascular fitness is a significant predictor of future success in a comprehensive behavioral weight loss program, but few studies have looked at the link between baseline fitness and future weight loss.

The study included 85 adults who were enrolled in an 18-month behavioral weight loss program that combined a calorie-restricted diet, group-based behavioral support, and 6 months of supervised exercise that progressed to 300 minutes per week of moderate-intensity exercise.

This program was followed by 12 months of unsupervised exercise.

The investigators used data from the 60 adults who completed the 18-month program in the final analysis of the study. They measured moderate-to-vigorous physical activity over 1 week using the Sensewear Armband at baseline and months 6, 12, and 18.

Fitness (VO₂max) was also measured on a treadmill using indirect calorimetry and categorized based on published age and sex norms (Physical Fitness Specialist Certification Manual, 1997).

The investigators used a linear mixed effects model with unstructured covariance to examine the association between baseline fitness category and changes in body weight, total moderate-to-physical activity, and moderate-to-vigorous activity in bouts ≥10 minutes at the 4 time points.

Of the individuals who completed the program, 20 were classified as having very poor fitness, 27 were deemed poor, 11 were labeled fair, and only 2 were classified as good. There were not any participants that were labeled as having excellent or superior fitness at baseline.

Because of the low proportion participants having fair or better fitness, the investigators created a binary fitness variable (very poor vs. poor or better). Baseline body mass index was higher in the very poor category when compared to those in the poor or better category (36.2±4.2 vs. 33.7±4.0; P = 0.03).

They found no significant differences between the 2 fitness categories in weight loss at 6 or 12 months, but the mean weight loss at 18 months was marginally significant between-group difference (P = 0.07).

There were also no differences in changes in total or bout moderate-to-vigorous physical activity, but individuals with very poor fitness had lower bout moderate-to-vigorous physical activity at baseline compared to those with poor or better fitness (16±20 vs. 33±31 min/d; P = 0.03).

At 18 months, both groups increased their bout moderate-to-vigorous physical activity, but this remained lower in the very poor group compared to the poor or better group (24±29 vs. 42±29 min/d; P = 0.03).

Total moderate-to-vigorous physical activity followed a similar pattern to the results from bout moderate-to-vigorous physical activity.

"Baseline fitness may moderate 18-month weight loss, as those with very poor fitness lost less weight compared to those with poor or better fitness levels,” the authors wrote. “Those with poor or better fitness at baseline achieved significantly higher mean levels of MVPA at 18 months compared to those with very poor fitness. Participants with very poor fitness at baseline may require additional exercise support during a BWLP to achieve the high levels of MVPA recommended for weight loss maintenance.”