Why exercise helps maintain weight loss

The central rule of weight loss appears simple: when you take in fewer calories than you use, you lose weight.

However, putting that principle into action is rarely quite so straightforward.

As well as tracking calories or reducing portion sizes, many people include exercise in their weight-loss efforts to help create a larger energy deficit. Research suggests, however, that exercise may have only a limited effect on the amount of weight lost.

That does not mean abandoning your workouts is a good idea. Exercise remains highly important for health and may be particularly valuable for preventing weight regain once you have reached your target weight.

A number of processes help explain why being active does not invariably lead to substantial weight loss.

Exercise can increase appetite and, in turn, food consumption. After a workout, people may also unconsciously be less active for the rest of the day, reducing the effect that exercise has on their total calorie deficit.

Over time, the body also becomes more economical, using fewer calories to complete the same activity. Known in some cases as "metabolic adaptation", this process reflects the body's natural drive to resist weight loss.

From an evolutionary standpoint, preserving energy during periods of heavy physical activity may have helped our ancestors avoid starvation. In the modern world, though, metabolic adaptation is among the many reasons weight loss can be challenging.

Exercise and maintaining weight loss

While exercise may not be the chief cause of weight loss, it appears to have a role in helping people maintain weight loss.

One study involving more than 1,100 people found that physical activity had little influence on how much weight participants initially lost. But higher activity levels after weight loss were strongly associated with keeping that weight off.

Exercise was also linked with measurable improvements in health, including improved cholesterol, less inflammation, better blood glucose management and greater insulin sensitivity. Each of these is associated with a lower risk of conditions including heart disease and type 2 diabetes.

These broad health gains underline the importance of exercising both during weight loss and while maintaining weight loss.

Research further indicates that pairing exercise with weight-loss medicines, such as Saxenda, may enable people to maintain their weight loss more effectively than taking the medicine alone.

Why exercise helps prevent weight regain

It can seem contradictory that exercise is not particularly effective for weight loss, yet may help stop weight from returning. Although the full explanation for this paradox is not known, several possible mechanisms may account for it.

The first concerns resting energy expenditure: the number of calories the body burns while at rest.

After weight loss, resting energy expenditure falls by more than would be expected from the weight lost alone. This is believed to be one factor behind weight regain. Exercise increases total daily energy expenditure, which may partly counteract that fall.

Muscle mass, metabolism and fat burning

Muscle mass is another important consideration.

Losing weight typically means losing both fat and muscle. As muscle loss reduces resting energy expenditure, it can make weight regain more likely.

Exercise, particularly resistance training such as Pilates or weight lifting, can help retain or even restore muscle mass. In turn, this may increase metabolism and support long-term weight maintenance.

Physical activity also supports the body's capacity to burn fat. Following weight loss, the body often becomes less effective at using fat as an energy source.

Intense exercise, however, may improve fat burning and metabolic flexibility - the capacity to alternate between using carbohydrates and fat depending on what is available. This enables the body to keep using fat for energy even when calorie intake is lower or weight has been lost.

Exercise also improves insulin sensitivity, meaning less insulin is needed to control blood glucose. This matters because higher insulin levels can encourage fat storage and limit the breakdown of fat.

Exercise, appetite and individual responses

Exercise can also influence weight maintenance indirectly. For example, it may improve sleep and mood while lowering stress. Together, these effects can reduce levels of cortisol, the stress hormone, which could decrease the amount of fat stored by the body.

Regular activity may additionally help control appetite and blood glucose, potentially easing cravings and reducing overeating.

It is important to recognise that responses differ between individuals. We do not all react to exercise in the same way, whether that concerns the calories we burn or whether a workout leaves us hungrier later in the day.

Different forms of exercise bring distinct benefits for health and weight maintenance too.

Aerobic exercise, including brisk walking, cycling and running, uses calories and may, at greater intensities, improve the body's ability to use fat as fuel.

Resistance training, by contrast, helps develop and retain muscle mass. This maintains a higher resting energy expenditure and supports long-term weight maintenance.

Exercise may not be the strongest tool for weight loss, but it can help preserve hard-won weight loss. More importantly, it delivers physical and mental health benefits that extend far beyond the figure on the scales.

Rachel Woods, Senior Lecturer in Physiology, University of Lincoln

This article is republished from The Conversation under a Creative Commons licence. Read the original article.