When people try to lose weight by eating less, their bodies often fight back by burning fewer calories and losing muscle along with fat. Scientists tested a new diabetes drug called semaglutide on obese pigs to see if it could help. After 10 weeks, pigs that took semaglutide lost weight in a healthier way—keeping more muscle and maintaining their metabolism—compared to pigs that only ate less food. This suggests the drug might help people lose fat while protecting the muscle they need to stay strong and healthy.

The Quick Take

  • What they studied: Whether a weight-loss drug called semaglutide could help prevent the muscle loss and metabolism slowdown that normally happens when people diet
  • Who participated: 24 obese Göttingen minipigs (a special breed used in medical research because their bodies work similarly to humans) divided into three groups: one that ate normally, one that took semaglutide and ate normally, and one that ate less food
  • Key finding: After 10 weeks, pigs on semaglutide lost weight while keeping more muscle and burning more calories than pigs that only dieted. Diet-only pigs lost 4.3 kg more muscle and burned 273 fewer calories per day, even though both groups lost similar amounts of weight
  • What it means for you: This suggests semaglutide might help people lose weight in a healthier way by protecting muscle and keeping metabolism active. However, this was tested in pigs, so more research in humans is needed before drawing firm conclusions

The Research Details

Scientists used 24 obese minipigs because their bodies process food and store fat similarly to humans. They divided the pigs into three equal groups of 8. One group ate as much as they wanted and received a placebo (fake treatment). The second group ate as much as they wanted but received semaglutide, a drug that helps control appetite and blood sugar. The third group ate less food (restricted diet) to match the weight loss of the semaglutide group, but received a placebo.

Over 10 weeks, researchers measured how much body fat and muscle each pig had, how many calories they burned, and looked at their blood work. At the end, they examined the pigs’ muscle tissue under a microscope to understand how the drug affected the cells that produce energy.

This design allowed scientists to compare three different approaches: normal eating, taking the drug while eating normally, and eating less food. By matching the weight loss between the drug group and the diet group, they could see if the drug helped preserve muscle and metabolism in ways that simple calorie restriction couldn’t.

When people diet, their bodies naturally try to conserve energy by burning fewer calories and breaking down muscle for fuel. This makes it harder to keep weight off long-term and can leave people feeling weak. Understanding whether semaglutide prevents these problems is important because it could lead to better weight-loss strategies that keep people healthy and strong. Using minipigs is valuable because their bodies work much like human bodies, making the results more likely to apply to people.

This study was published in a respected scientific journal focused on metabolism and energy. The researchers used careful measurements of body composition and energy expenditure, and examined tissue at the cellular level. However, this was an animal study, so results may not directly apply to humans. The sample size was relatively small (24 animals total), which is typical for this type of detailed research. The study was well-controlled, with clear comparison groups, which strengthens the reliability of the findings.

What the Results Show

The most important finding was that semaglutide protected muscle while promoting fat loss. Pigs that only dieted lost 4.3 kg more muscle than pigs taking semaglutide, even though both groups lost similar total weight. This means the diet-only group lost more muscle and less fat, while the semaglutide group lost more fat and kept more muscle—a much healthier outcome.

Semaglutide also helped maintain metabolism. Diet-only pigs burned 273 fewer calories per day compared to pigs eating normally, suggesting their bodies had slowed down to conserve energy. Pigs taking semaglutide didn’t show this slowdown, meaning their bodies kept burning calories at a normal rate.

When scientists looked at the muscle cells, they found that diet restriction caused specific changes that make cells burn fewer calories. Semaglutide prevented these energy-saving changes, which helps explain why the drug group maintained better metabolism. The drug appeared to work by keeping the body’s energy-burning machinery running normally, rather than allowing it to shift into a ‘conservation mode’ like dieting alone does.

Researchers also measured blood sugar control and other metabolic markers. The semaglutide group showed improvements in these measures, which is expected since the drug is designed to help regulate blood sugar. The diet-only group showed signs of metabolic adaptation—their bodies were adjusting to conserve energy, which is a normal but potentially problematic response to calorie restriction. These secondary findings support the main conclusion that semaglutide works through different mechanisms than simple calorie restriction.

Previous research has shown that dieting alone often leads to muscle loss and a slower metabolism, making weight regain common. Some earlier studies suggested that GLP-1 drugs like semaglutide might help with weight loss, but this is one of the first studies to specifically examine whether it protects muscle and prevents the metabolic slowdown that normally occurs with dieting. The findings align with what researchers expected based on how the drug works in the body, and they provide new details about the specific cellular mechanisms involved.

This study was conducted in minipigs, not humans, so the results may not translate exactly to people. The study lasted only 10 weeks, which is relatively short for understanding long-term effects. The sample size was small (8 pigs per group), which is typical for detailed laboratory studies but means results should be confirmed in larger studies. The researchers didn’t test different doses of semaglutide or different lengths of treatment, so it’s unclear how these factors might affect the results. Finally, this was a controlled laboratory setting, not real-world conditions, so factors like stress, activity level variations, and food choices weren’t included.

The Bottom Line

Based on this research, semaglutide appears promising for weight loss that preserves muscle and maintains metabolism. However, this is animal research, and human studies are needed before making clinical recommendations. If considering semaglutide for weight loss, discuss it with a healthcare provider who can evaluate individual health status, potential side effects, and whether it’s appropriate. This drug should be combined with healthy eating and physical activity for best results. Confidence level: Moderate—the research is well-designed but limited to animal studies.

This research is most relevant to people with obesity who are struggling with weight loss, particularly those concerned about losing muscle or experiencing a metabolism slowdown during dieting. Healthcare providers treating obesity should be aware of these findings. People with type 2 diabetes may find this especially relevant since semaglutide is already used for blood sugar control. This research is less directly applicable to people at a healthy weight or those with other health conditions, though the underlying mechanisms may have broader relevance.

In the minipig study, significant differences appeared within 10 weeks. If similar effects occur in humans, people might expect to see benefits within several weeks to a few months. However, individual results vary, and it typically takes 3-6 months to see substantial changes in body composition (fat vs. muscle). Maintaining these benefits likely requires continuing the medication and healthy lifestyle habits long-term.

Want to Apply This Research?

  • Track weekly weight, but more importantly, monitor body measurements (waist, chest, arms, thighs) and how clothes fit. Use a simple scale or measuring tape weekly. This reveals whether weight loss is coming from fat or muscle—the app could show trends in measurements alongside weight to highlight healthy fat loss.
  • Users taking semaglutide should prioritize protein intake (chicken, fish, eggs, beans) at each meal to support muscle preservation. The app could send reminders to log protein intake and set daily protein goals. Users should also track resistance exercise (weight training or bodyweight exercises) 2-3 times weekly, as this helps maintain muscle during weight loss.
  • Create a monthly body composition check-in that combines weight, measurements, and strength assessments (like how many push-ups or squats someone can do). Track energy levels and metabolism indicators like resting heart rate. The app could show a dashboard comparing fat loss vs. muscle preservation over time, helping users see that healthy weight loss is happening even if the scale moves slowly.

This research was conducted in minipigs and has not yet been tested in humans. Semaglutide is a prescription medication that should only be used under medical supervision. This article is for educational purposes and should not be considered medical advice. Anyone considering semaglutide or other weight-loss treatments should consult with a qualified healthcare provider to discuss potential benefits, risks, side effects, and whether it’s appropriate for their individual health situation. Results in animals may not directly translate to humans. Always follow your doctor’s guidance regarding medication use and weight management.