While exercise is widely incorporated into weight loss strategies, new research indicates that its primary strength may lie more in maintaining weight loss and conferring broader health benefits, rather than in facilitating initial pound reduction.
The fundamental principle of weight loss—consuming fewer calories than are burned—is straightforward in theory but often challenging in practice. Many individuals integrate exercise alongside dietary changes to create a calorie deficit, yet studies suggest its direct impact on significant weight loss can be modest.
However, experts caution against dismissing workouts. Exercise remains crucial for overall health and appears to play an especially vital role in preventing weight regain after an individual has reached their target weight.
Several physiological processes help explain why exercise may not always lead to substantial weight loss. Physical activity can stimulate appetite, potentially leading to increased food intake. Furthermore, individuals might unconsciously reduce their general movement throughout the rest of the day after a workout, which can diminish the overall calorie deficit achieved through exercise.
The body also adapts over time, becoming more efficient at burning fewer calories for the same activity. This process, known as "metabolic adaptation," reflects the body's inherent tendency to defend against weight loss. From an evolutionary perspective, conserving energy during periods of intense physical activity would have protected ancestors from starvation. In a contemporary context, metabolic adaptation is one of many factors that can complicate weight loss efforts.
Despite its less prominent role in initial weight loss, exercise appears to be a significant factor in weight maintenance. A study involving over 1,100 people found that while physical activity had little effect on the amount of weight initially lost, higher levels of activity post-weight loss were strongly associated with maintaining that loss.
Beyond weight management, exercise is linked to a range of measurable health improvements. These include better cholesterol levels, reduced inflammation, improved blood sugar control, and enhanced insulin sensitivity. All these factors are associated with a lower risk of serious health problems such as heart disease and type 2 diabetes, underscoring the importance of regular physical activity during both weight loss and maintenance phases.
Evidence also suggests that combining exercise with weight loss medications, such as Saxenda, may lead to better long-term weight maintenance outcomes compared to using the drug alone.
The reasons behind this apparent paradox—that exercise is less effective for losing weight but helpful in preventing regain—are not yet fully understood, but several mechanisms have been proposed.
One explanation involves resting energy expenditure (REE), the calories the body burns at rest. After weight loss, REE often decreases by more than would be expected for the amount of weight lost, which can contribute to weight regain. Exercise, however, raises total daily energy expenditure, helping to partially offset this reduction.
Weight loss typically involves the reduction of both fat and muscle mass. Losing muscle lowers REE, further contributing to the risk of weight regain. Resistance training, which includes activities like Pilates or lifting weights, can help preserve or even rebuild muscle mass. This, in turn, can boost metabolism, supporting long-term weight maintenance.
Physical activity also helps the body maintain its ability to burn fat for energy. After weight loss, the body can become less efficient at utilising fat as fuel. Intense exercise, however, can enhance fat burning and improve metabolic flexibility—the body’s capacity to switch between burning carbohydrates and fat depending on availability. This mechanism assists the body in continuing to burn fat even when calorie intake is low or weight has been lost.
Furthermore, exercise improves insulin sensitivity, reducing the amount of insulin required to regulate blood sugar. This is beneficial because higher insulin levels can promote fat storage and hinder fat breakdown.
Exercise also exerts numerous indirect effects that can aid in weight maintenance. For example, it can improve sleep quality, elevate mood, and reduce stress levels. These benefits help lower levels of the stress hormone cortisol, which could potentially reduce the amount of fat the body stores. Regular physical activity can also help regulate appetite and blood glucose, which may assist in reducing cravings and limiting overeating.
It is important to acknowledge individual differences; people respond uniquely to exercise in terms of calorie expenditure or how a workout affects subsequent hunger levels.
Different types of workouts offer distinct benefits for health and weight maintenance. Aerobic exercise, such as brisk walking, cycling, or running, burns calories and, at higher intensities, can enhance the body's capacity to burn fat. Resistance training, conversely, is key for building and preserving muscle mass, which supports a higher resting energy expenditure and aids in long-term weight maintenance.
While exercise may not be the most potent tool for initial weight loss, its critical role in sustaining hard-earned reductions and providing extensive physical and mental health benefits extends far beyond the numbers on a scale.
This article is based on materials provided by The Conversation, originally written by Rachel Woods, Senior Lecturer in Physiology at the University of Lincoln. Content may have been edited for style and length.
