A new study conducted at the Gray Faculty of Medical and Health Sciences and the Sylvan Adams Sports Science Institute at Tel Aviv University reveals a clear conclusion: strength (resistance) training is the most effective tool for achieving “high-quality” weight loss, reducing body fat while preserving, and even increasing, muscle mass.
The study was led by Prof. Yftach Gepner, together with Yair Lahav and Roi Yavetz, and was published in the scientific journal Frontiers in Endocrinology . The researchers analyzed data from hundreds of women and men aged 20–75 who participated in a structured weight-loss program. All participants adhered to a low-calorie diet with a controlled energy deficit but were divided into three groups based on their chosen activity: no physical exercise, aerobic exercise, or resistance training.
The findings show that while total weight loss was similar across all groups, a significant difference was found in the composition of the weight loss. Participants who performed strength training lost more fat than those in the other groups, and at the same time were the only ones who succeeded in preserving and even increasing their muscle mass. In contrast, participants who did not exercise, as well as those who engaged in aerobic activity alone, lost a substantial portion of their muscle mass as part of the weight-loss process.
The research team explains: “Although total weight loss was similar among all participants, the key difference lay in the composition and quality of that loss. While weight loss without strength training, and even with aerobic activity alone, was accompanied by loss of muscle mass, strength training led to weight loss based primarily on loss of fat, while preserving and even increasing muscle mass. This means that weight loss achieved through strength training is not just a decrease on the scale, but a healthier, more stable, and more effective long-term process.”
Muscle mass plays a central role in health and metabolism. Muscle constitutes about 40% of body weight and is responsible for a significant portion of daily energy expenditure, even at rest. When muscle mass declines, metabolic rate decreases, weight loss becomes more difficult, and the likelihood of regaining weight after dieting increases. Therefore, weight loss that does not preserve muscle may be less sustainable and potentially harmful in the long term.
Beyond that, maintaining muscle mass is essential for everyday functioning, strength, stability, and balance. Loss of muscle can impair physical ability, increase the risk of injuries and falls, and may even accelerate the development of sarcopenia age-related muscle degeneration that can also affect relatively young individuals during unbalanced dieting.
The study also demonstrated a clear advantage of strength training in reducing waist circumference a key indicator of abdominal obesity and cardiometabolic risk. The greatest reductions in waist circumference were observed among the participants who engaged in strength training and were found to be strongly associated with fat loss, highlighting this type of exercise’s contribution to heart and metabolic health.
According to the researchers, the findings underscore that not all weight loss is equal in quality. “Good” weight loss reduces body fat, preserves muscle, and supports health and long-term weight maintenance. The study’s conclusion is clear: incorporating strength training into weight-loss programs is not a luxury, but an essential component of healthy, effective, and sustainable weight loss for both women and men.
Prof. Gepner concludes: “Our study shows that weight loss should not be measured only by how many kilograms we lose, but by the quality of that loss. When appropriate nutrition is combined with strength training, it is possible to reduce fat effectively while preserving and even improving muscle mass, a critical factor for metabolic health, daily functioning, and long-term weight maintenance. Our findings make it clear that strength training is not just for athletes, but a vital tool for anyone who wants to lose weight in a healthy, safe, and sustainable way, women and men alike.”
Link to the article:
https://www.frontiersin.org/journals/endocrinology/articles/10.3389/fendo.2025.1725500/full
Frontiers in Endocrinology