Structured Exercise Essential for Fitness Gains Alongside Weight-Loss Medication
A recent study published in the journal Sports Medicine indicates that structured exercise is the primary contributor to improvements in physical fitness during long-term weight maintenance, even when weight loss is supported by glucagon-like peptide-1 receptor agonist (GLP-1 RA) therapy. While GLP-1 RAs effectively facilitate weight reduction, they did not independently enhance physical fitness, mobility, or cardiorespiratory health without concurrent exercise.
The findings suggest that combining weight-loss medications with a structured exercise program is crucial for optimizing functional health outcomes in adults with obesity.
Background
Obesity affects over 650 million adults worldwide and is associated with reduced mobility and cardiorespiratory fitness. Advances in pharmacotherapy, such as GLP-1 RAs, have shown efficacy in weight loss. However, concerns have been raised regarding whether pharmacotherapy-induced weight loss alone leads to significant improvements in physical fitness, particularly given potential reductions in fat-free mass.
This study aimed to investigate the individual and combined impacts of structured exercise and GLP-1 RA therapy on physical fitness during long-term weight maintenance following an initial period of diet-induced weight loss.
Study Design and Participants
This secondary analysis utilized data from a randomized, placebo-controlled clinical trial. It included adults aged 18 to 65 with obesity (Body Mass Index between 32-43 kg/m²) who did not have diabetes. Participants first underwent an 8-week, 800-kcal/day low-calorie diet. Only those who achieved at least a 5% reduction in body weight were subsequently randomized.
Intervention Groups
Over a period of 52 weeks, participants were allocated to one of four intervention groups:
- Placebo with usual physical activity.
- Placebo with structured exercise.
- Liraglutide (a GLP-1 RA) at a dose of 3.0 mg daily, with gradual dose escalation for tolerability, alongside usual physical activity.
- Liraglutide combined with structured exercise.
Exercise Program and Assessments
The structured exercise program adhered to World Health Organization (WHO) recommendations, involving approximately 108 minutes of moderate-to-vigorous physical activity per week. This included supervised group interval cycling and circuit training, supplemented by individual moderate-to-vigorous activities. Heart rate devices were used to monitor exercise intensity. Participants in exercise groups completed a median of 2.65 sessions per week.
Physical fitness assessments were conducted at baseline, after the low-calorie diet phase, and following 52 weeks of intervention. These assessments included:
- Stair-climb performance.
- Cardiorespiratory fitness, measured by peak oxygen consumption (VO₂peak).
- Muscle strength, measured by maximal isometric knee extensor torque.
Key Findings
A total of 193 participants were randomized into the study, with approximately 85% completing the 52-week intervention.
Physical Function and Mobility
Improvements in physical functional performance were primarily observed in the groups that included structured exercise. The group receiving combined exercise and Liraglutide completed the stair-climb test significantly faster than those receiving Liraglutide alone or placebo. Exercise alone also led to comparable improvements in stair-climb performance. Liraglutide alone did not result in an improvement in stair-climb performance, despite sustained weight loss. Participants in the combined treatment group also reported greater ease with intensive daily tasks such as lifting groceries, walking, bending, or dressing.
Cardiorespiratory Fitness
Cardiorespiratory fitness (VO₂peak relative to fat-free mass) increased by approximately 10% in both the structured exercise-only group and the combined exercise and Liraglutide treatment group. Liraglutide alone did not show a statistically significant improvement in this measure compared to placebo. Exercise also enhanced absolute VO₂peak and maximal cycling power.
Muscle Strength and Quality
Muscle strength, assessed by maximal knee extensor torque, remained stable across all groups. However, strength relative to body weight improved in all active treatment groups, a change attributed to the reduction in body weight. While muscle quality declined in the placebo group, it was maintained in participants who either exercised or received Liraglutide.
Exercise Volume and Functional Outcomes
Analyses indicated a dose-response relationship, where a greater volume of moderate-to-vigorous exercise correlated with superior functional outcomes. Each additional 10 minutes of weekly exercise was associated with faster stair-climb performance and higher VO₂peak relative to fat-free mass.
Implications for Obesity Management
The study concluded that structured moderate-to-vigorous exercise is the primary factor driving improvements in physical fitness during long-term weight maintenance, even when weight loss is supported by GLP-1 RA therapy. While GLP-1 RAs are effective for weight loss, they were found to be insufficient in significantly improving physical fitness without concurrent exercise. Structured exercise, whether implemented alone or in combination with pharmacotherapy, resulted in clinically meaningful gains in mobility, cardiorespiratory fitness, and functional independence.
These findings suggest that for adults with obesity, combining weight-loss medications with structured exercise programs is important for optimizing functional health outcomes, rather than solely focusing on weight reduction.