Why Exercise Helps Maintain Weight Loss

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

Putting that rule into practice, however, is rarely quite so straightforward.

As well as tracking calories or reducing portion sizes, many people turn to exercise when trying to lose weight, hoping it will help create a greater deficit. Research suggests, though, that exercise may have only a limited effect on weight loss itself.

That does not mean you should abandon your workouts. 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 explain why exercising does not necessarily lead to large amounts of weight loss.

Working out can increase appetite, causing people to eat more. After exercise, people may also unconsciously be less active for the remainder of the day, reducing the effect of their workout on their total calorie deficit.

Over time, the body can also become more efficient, using fewer calories to perform the same activity. Known at times as "metabolic adaptation", this process reflects the body's inclination to resist weight loss.

From an evolutionary standpoint, saving energy during spells of strenuous activity may have helped protect our ancestors from starvation. In the modern world, however, metabolic adaptation is one of several factors that can make losing weight harder.

The importance of exercise

While exercise may not be the primary force behind weight loss, it appears to have a role in helping people maintain weight loss.

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

Exercise was also linked with measurable health gains, including improved cholesterol, reduced inflammation, better blood sugar management and greater insulin sensitivity. Each of these is associated with a lower risk of conditions such as heart disease and type 2 diabetes.

These wide-ranging health advantages underline the value of being active both during weight loss and while maintaining it.

Research also indicates that combining exercise with weight-loss medicines, such as Saxenda, may help people keep weight off more effectively than taking the medicine by itself.

Why exercise works

It may seem puzzling that exercise is not especially powerful for weight loss but can help stop weight from returning. The reasons for this apparent contradiction are not completely clear, although several mechanisms may explain it.

The first concerns resting energy expenditure: the number of calories the body uses 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 contribute to weight regain. Exercise increases total daily energy expenditure, however, and can partly counteract this reduction.

A second explanation involves muscle mass.

Losing weight generally means losing muscle as well as fat. Because muscle loss lowers resting energy expenditure, it can make weight regain more likely.

Exercise, particularly resistance training such as Pilates or weightlifting, can help retain and even restore muscle mass. This may raise metabolism and support long-term weight maintenance.

Physical activity also helps the body preserve its capacity to use fat as fuel. Following weight loss, the body frequently becomes less effective at burning fat for energy.

Intense exercise, however, can improve fat burning and metabolic flexibility - the capacity to shift between using carbohydrates and fat according to availability. This enables the body to keep burning fat even when calorie consumption is low or weight has been lost.

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

There are many indirect ways in which exercise can support weight maintenance. For example, it can enhance sleep and mood while lowering stress. Together, these effects reduce levels of the stress hormone cortisol, which may decrease the amount of fat stored by the body.

Regular activity may also regulate appetite and blood glucose, potentially reducing cravings and helping to curb overeating.

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

Various forms of exercise also provide distinct benefits for health and weight maintenance.

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

Resistance training, by contrast, helps to build and preserve muscle. 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 provides physical and mental health benefits that extend far beyond the number 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.