Researchers studied 193 adults with obesity to see how exercise and a weight loss medication called liraglutide affected their fitness. After everyone lost weight through dieting, some did exercise, some took the medication, some did both, and some did neither. The study found that exercise—either alone or combined with the medication—significantly improved how quickly people could climb stairs and how well their hearts and lungs worked. Interestingly, the medication alone didn’t improve fitness much, but it did help preserve muscle when combined with exercise. This suggests that moving your body is crucial for getting physically stronger, even when taking weight loss medications.

The Quick Take

  • What they studied: Whether exercise and/or a weight loss medication called liraglutide could improve physical fitness (strength, heart health, and ability to move around) in people with obesity after they lost weight through dieting.
  • Who participated: 193 adults aged 18-65 years old with obesity (BMI between 32-43) who didn’t have diabetes. Everyone first completed an 8-week diet program, then was randomly assigned to one of four groups: exercise only, medication only, exercise plus medication, or neither.
  • Key finding: Exercise—whether done alone or combined with the medication—improved how fast people could climb stairs (about 8.6% faster) and improved their heart and lung fitness. The medication alone didn’t improve these fitness measures, but when combined with exercise, it helped people keep more muscle while losing weight.
  • What it means for you: If you’re trying to lose weight and get healthier, exercise appears to be essential for improving your actual physical fitness and strength. Weight loss medications may help you lose weight, but they work best when combined with regular exercise. This suggests you shouldn’t rely on medication alone—moving your body matters.

The Research Details

This was a carefully designed experiment where 193 people with obesity were split into four equal groups. Everyone first went on a strict diet for 8 weeks and lost weight. Then, for the next year, one group exercised regularly, one group took a daily injection of liraglutide (a medication that helps with weight loss), one group did both exercise and took the medication, and one group did neither (control group).

The exercise program was fairly intense—people did indoor cycling with interval training (going fast, then slow, then fast again) combined with circuit training (moving between different exercises). They exercised about 2-3 times per week for roughly 2 hours total, working hard enough that their heart rate was around 79% of maximum. Researchers tracked how much people actually exercised using sports watches and heart rate monitors.

The researchers measured three important fitness measures: how quickly people could climb stairs (up and down 11 steps twice), how well their heart and lungs worked (measured by oxygen consumption), and how strong their leg muscles were. They measured these at the start and end of the year-long study.

This research design is strong because it randomly assigned people to different groups, which helps prove that the results come from the treatments themselves, not from differences between people. The researchers also carefully tracked exercise using technology rather than just asking people if they exercised. By measuring actual fitness improvements (not just weight loss), they could see what really matters for health.

This is a high-quality study because: (1) it’s a randomized controlled trial, which is considered the gold standard in research; (2) it had a good number of participants (193); (3) it lasted a full year, long enough to see real changes; (4) researchers used objective measurements (timed tests, oxygen consumption, strength tests) rather than relying on what people reported; (5) they tracked exercise with devices to ensure people actually did it. The main limitation is that it only included people without diabetes, so results may not apply to everyone.

What the Results Show

Exercise made a real difference in fitness. People who exercised could climb stairs about 1.2 seconds faster (8.6% improvement) compared to those who only took the medication. Their heart and lung fitness also improved by about 3 milliliters of oxygen per minute per kilogram of muscle—a meaningful improvement that means their cardiovascular system worked more efficiently.

When people combined exercise with the medication, they got similar improvements to exercise alone in stair climbing and heart-lung fitness. This suggests that the medication didn’t add extra fitness benefits on top of exercise, but it also didn’t interfere with exercise benefits.

The medication alone (without exercise) didn’t improve these fitness measures. People who only took the medication without exercising didn’t climb stairs faster or improve their heart-lung fitness compared to the control group.

For muscle strength, the picture was slightly different. Everyone lost muscle relative to their body weight because they lost weight overall. However, people who exercised, took the medication, or did both preserved more absolute strength (actual muscle power) than those who did neither. When strength was adjusted for body weight, the medication and exercise groups maintained better relative strength because they kept more muscle while losing fat.

The study found that exercise adherence (how consistently people exercised) was good and similar whether people took the medication or placebo. People exercised about 2.65 times per week for 116 minutes total, working at the right intensity level. This shows that the medication didn’t make people more or less likely to stick with exercise. The combination of exercise and medication was well-tolerated, with no unexpected safety issues reported.

This research supports what scientists have long believed: exercise is crucial for improving physical fitness and health, not just for losing weight. Previous studies showed that weight loss medications help people lose weight, but this study adds important evidence that these medications don’t automatically make you stronger or improve your heart-lung fitness. The finding that exercise alone was as effective as exercise plus medication for fitness improvements suggests that the medication’s main benefit is weight loss, which can then help with other health measures. This aligns with other research showing that multiple approaches (diet, exercise, and medication) work best together.

This study only included adults aged 18-65 without diabetes, so results may not apply to older adults or people with diabetes. The study lasted one year, so we don’t know if benefits continue longer or if people maintain their fitness after the study ends. The exercise program was fairly intense and structured, so results might differ for people doing less intense or less organized exercise. The study didn’t include people with very severe obesity, so results may not apply to that group. Finally, this was a secondary analysis (looking at fitness data from a larger study about weight loss), so it wasn’t originally designed to study fitness as the main outcome.

The Bottom Line

If you want to improve your physical fitness and strength after weight loss, exercise should be your priority. The evidence strongly suggests that moderate-to-vigorous exercise (like the cycling and circuit training in this study) is essential for improving how strong you are and how well your heart and lungs work. Weight loss medications like liraglutide may help you lose weight, but they don’t replace the fitness benefits of exercise. If you’re considering a weight loss medication, combining it with regular exercise appears to be the best approach. Aim for about 2-3 exercise sessions per week at a moderate-to-vigorous intensity (where you’re working hard but can still talk). Confidence level: High for exercise benefits; Moderate for medication benefits when combined with exercise.

This research is most relevant for adults with obesity who have lost weight and want to improve their fitness and strength. It’s particularly important for people considering weight loss medications—it shows that medication alone won’t make you stronger or improve your heart health. People without obesity probably won’t need this information, though the exercise recommendations apply to everyone. If you have diabetes or are older than 65, talk to your doctor before starting an intense exercise program, as this study didn’t include those groups.

Based on this study, you should expect to see improvements in stair climbing ability and heart-lung fitness within weeks to a few months of consistent exercise. The study measured changes over a full year, but meaningful improvements likely appear sooner. Muscle strength improvements may take longer to notice. Don’t expect the medication alone to improve your fitness—its main benefit is helping with weight loss, which can indirectly help your health.

Want to Apply This Research?

  • Track weekly exercise sessions and intensity level (using heart rate or perceived effort). Specifically, log: (1) number of exercise sessions per week (goal: 2-3), (2) total weekly exercise minutes (goal: 100-150 minutes), (3) average heart rate during exercise (goal: 70-85% of maximum), and (4) monthly stair climb time (climb 11 steps up and down, time yourself, and track if it’s getting faster).
  • Set a specific exercise schedule: pick 2-3 days per week for structured workouts combining cardio (like cycling or running) with strength training (like circuit training or weights). Start with your current fitness level and gradually increase intensity. If taking a weight loss medication, use the app to remind you to take it consistently while also scheduling your exercise sessions—treat them as equally important.
  • Create a dashboard showing: (1) weekly exercise adherence (sessions completed vs. goal), (2) monthly stair climb test results (track if times are improving), (3) subjective fitness improvements (can you walk further without getting tired? Can you carry groceries easier?), and (4) consistency over time (are you maintaining exercise habits after 3 months, 6 months, 1 year?). Set monthly check-ins to review progress and adjust intensity if needed.

This research summary is for educational purposes only and should not replace professional medical advice. Before starting any new exercise program or weight loss medication, consult with your doctor or healthcare provider, especially if you have existing health conditions, take medications, or are pregnant or breastfeeding. The findings apply specifically to adults aged 18-65 without diabetes; results may differ for other populations. Individual results vary based on genetics, starting fitness level, diet, and consistency with exercise. This study was conducted over one year; long-term effects beyond this timeframe are unknown. Always work with qualified fitness professionals and healthcare providers to develop a safe, personalized plan.