Weight loss cannot be done with just exercise; it can even cause increased fat: Doctor explains why

Many people believe that regular exercise is the key to losing weight. From gym workouts to fitness apps, the message often is that burning more calories through physical activity will help shed pounds. However, recent insights from experts suggest this common belief is misleading. Exercise alone, without changes to diet and lifestyle, is unlikely to cause significant weight loss.

Limitations of Exercise in Weight Management

Tim Spector, a respected and award-winning British epidemiologist specializing in gut health and diet, explains that long-term research consistently shows exercise alone does not produce meaningful weight loss. Physical activity can help prevent weight gain but is not effective at reducing body fat without accompanying dietary changes. He points out that exercise helps maintain weight once lost but is not a reliable method to lose weight on its own.

He also criticizes the common fitness narrative pushed by gyms and wellness apps, which often suggest that people can eat whatever they want as long as they work out enough. Spector calls this approach misleading and states that it overlooks the critical role of diet in weight control.

Diet: The Cornerstone of Weight Loss
The epidemiologist stresses that diet is the most important factor in losing weight. Consuming a balanced diet rich in vegetables, fruits, and whole grains, and maintaining a calorie deficit are essential for reducing body fat. Changing eating habits is necessary for weight loss, and exercise complements these changes rather than replaces them.

Spector warns against simplistic explanations that blame single dietary components like sugar for weight gain. Instead, he views weight management as a complex issue influenced by overall diet quality and energy balance.

Exercise Can Sometimes Work Against Weight Loss

Interestingly, exercise may increase hunger and prompt people to eat more, which can negate the calories burned during a workout. This biological response is part of the body's effort to restore energy after physical activity. Therefore, without mindful eating, exercising could lead to increased calorie intake that cancels out any deficit created by movement.

While exercise may not be the magic solution for weight loss, Spector acknowledges its numerous other benefits. Regular physical activity improves cardiovascular health, enhances mood, boosts stamina, and even offers protection against some cancers. He encourages people to stay active for these reasons but clarifies that for those aiming to lose weight, focusing on diet is indispensable.

( Originally published on Aug 09, 2025 )