Participants who had higher levels of fitness when beginning a behavioral weight-loss intervention kept off more weight over the course of an 18-month study, compared with those with lower levels of fitness at baseline.
Those with higher baseline fitness also were able to achieve higher levels of moderate to vigorous physical activity at the 18-month mark, Adnin Zaman, MD, said during a virtual news conference held by the Endocrine Society. The study had been slated for presentation during ENDO 2020, the society's annual meeting, which was canceled because of the COVID-19 pandemic.
"Our study really comes from an observation that we often see significant variability in how much weight participants lose during a behavioral weight-loss intervention study," said Dr. Zaman, an endocrinology research fellow at the University of Colorado at Denver, Aurora.
She and her colleagues wanted to look at baseline cardiovascular fitness as an individual-specific factor that could affect how much weight people lost when participating in a behavioral intervention.
"Very little is known about how cardiovascular fitness affects [people's] ability to lose weight [or] to adhere to high levels of physical activity, which is a very common recommendation during a program for both weight loss and weight-loss maintenance," she added.
Dr. Zaman and colleagues conducted a secondary analysis of data from an 18-month trial of behavioral interventions for weight loss. The trial randomized 170 participants 1:1 to receive either concurrent exercise and a dietary behavior modification intervention or sequential dietary and exercise interventions.
The 85 participants in the concurrent intervention arm received 18 months of combined dietary modifications (calorie-restricted diet and group-based behavioral support) and exercise (supervised for the first 6 months of the study, unsupervised for the final 12). Those participating in the sequential intervention arm received a diet-only intervention during the first 6 months of the study, after which supervised exercise was added to the dietary intervention for 6 months, followed by a final 6 months of unsupervised exercise.
Participants in both study arms worked up to 300 minutes a week of moderate to vigorous physical activity in the supervised exercise phase.
For the secondary analysis, Dr. Zaman and colleagues looked only at the 60 participants who received concurrent diet and exercise interventions and who completed the full 18-month study. The mean age in that group was 40 years, mean baseline body mass index (BMI) was 34.6 kg/m2, and 80% of participants in the group were women.
Cardiovascular fitness as measured by VO2max was assessed at baseline using a graded exercise test. Participants were designated as having either "very poor" or "poor or better" cardiovascular fitness (20 and 40 participants, respectively).
Participants in the original trial were inactive at baseline and had a BMI range of 27-42 kg/m2. Among the subset of participants studied by Dr. Zaman and colleagues, those who were in the poor or better fitness category actually weighed less at baseline and had a lower BMI, compared with those in the very poor group (33.7 vs. 36.2, respectively), she said. Mean VO2max for those with very poor fitness was 22.5 mL/kg per minute, compared with 25.6 mL/kg per minute for those with poor or better fitness.
"Despite those differences, it is interesting to note that, during the supervised exercise portion of the study ... everyone lost pretty much the same amount of weight in the first 6 months," said Dr. Zaman. At the 6-month mark, those with very poor fitness had lost 9.2 kg (20.3 pounds), and those with poor or better fitness had lost 9.1 kg (20.1 pounds). However, weight regain was less likely in those with poor or better fitness, and those participants had a net loss of weight from baseline of 8.2 kg (18.1 pounds), compared with 4.4 kg (9.7 pounds) for those with very poor fitness.
Those with poor or better fitness were able to sustain a 33-minute bout of moderate to vigorous physical activity at baseline, whereas those with very poor fitness could achieve only about half of that. The difference in achievable physical activity between the two groups persisted throughout the study, with a peak at the 6-month mark, at about 60 minutes for the more fit participants and 38 minutes for those in the poor fitness group. By the end of the study, the less-fit participants achieved about 24 minutes of activity, whereas those who were more fit could sustain about 42 minutes of moderate to vigorous physical activity.
Physical activity levels were measured with a validated, wrist-worn device during a 1-week period at baseline and again at study months 6, 12, and 18.
Dr. Zaman noted that baseline weight may have confounded fitness categorization, because VO2max includes body weight in its calculations. A newer method of calculating cardiorespiratory fitness that scales VO2max to body weight may help minimize this potential confounder.
The investigators reported no outside sources of funding and reported that they had no financial conflicts of interest.
The research will be published in a special supplemental issue of the Journal of the Endocrine Society. In addition to a series of news conferences on March 30-31, the society will host ENDO Online 2020 during June 8-22, which will present programming for clinicians and researchers.
SOURCE: Zaman A et al. ENDO 2020, Abstract 575.
This article originally appeared on MDedge.com.
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