Running to lose weight without losing muscle mass?

Running burns energy. That is why it naturally ranks among the first choices for people who decide to lose weight. But there is an important difference between losing weight and losing fat. When diet and training are not properly balanced, some of the pounds lost may come precisely from the muscle mass the runner would like to preserve.

The challenge increases when someone combines a high volume of running with an aggressive reduction in food intake. In this situation, the body has to cope simultaneously with the demands of training, recovery and a lower energy supply.

The answer is not simply “eat less and run more.” For those who want to lose weight while maintaining muscle and performance, reducing food intake is not the most important factor. What goes on the plate is the key consideration.

Calorie deficit: losing weight does not mean starving yourself

Weight loss occurs when, over time, energy expenditure exceeds energy intake. This is known as an energy deficit or calorie deficit. The problem arises when that difference becomes too large.

The International Olympic Committee consensus on Relative Energy Deficiency in Sport (REDs) draws attention to low energy availability: a situation in which, after the energy used during exercise is deducted, insufficient energy remains to adequately support the body’s functions. When prolonged, it can affect health and performance.

For runners who want to lose weight, this means that the deficit needs to be planned with training in mind. A study on weight loss and protein management in athletes proposes, as a practical guideline, a moderate deficit combined with adequate protein intake and resistance exercise to reduce fat while preserving so-called “lean mass” (fat-free mass). The appropriate amount is not universal: energy needs vary according to weight, body composition, sex, routine, and the volume and intensity of training.

Protein takes center stage when calories decrease

When less energy is available, protein deserves special attention. It provides amino acids used to maintain and repair muscle tissue, and the need for it may increase during periods of energy restriction.

The International Society of Sports Nutrition (ISSN) considers a daily intake of between 1.4 and 2.0 grams of protein per kilogram of body weight sufficient for most physically active people, while noting that higher amounts may be necessary during periods of energy restriction to help maintain fat-free mass. The organization also identifies, as a general guideline per meal, approximately 0.25 g/kg or around 20g to 40 g of high-quality protein.

In athletes undergoing weight loss, this study works with a range of 1.6 to 2.4 g/kg/day, depending, among other factors, on the intensity of the calorie restriction and the training performed.

In practice, this reinforces the importance of including protein sources in meals throughout the day. Beef, poultry, fish, eggs, milk and dairy products, and combinations of plant-based foods can all be part of this strategy, according to individual needs and preferences.

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What about carbohydrates? Cutting them out can backfire

When weight loss is the goal, carbohydrates often become the first thing to disappear from the plate. For runners, however, caution is needed.

Running increases energy demands, especially during higher-intensity and longer-duration workouts. If a runner sharply reduces both total calorie and carbohydrate intake at the same time, they may end up following a diet that is incompatible with their training load.

However, the type of macronutrient must also be taken into account. Less refined, fiber-rich options, such as oats, whole-grain breads and tubers, come with other nutrients and are digested more slowly, which helps maintain satiety for longer. Faster-digesting sources, such as white bread, ripe bananas, honey, sports drinks and carbohydrate gels, may be useful before or during certain workouts, when the body needs energy to become available quickly.

The amount, choice and timing of consumption should be aligned with the running routine and individual goal.

Read also: Sports nutrition: what to eat before and after running

Run to lose weight, strength train to protect muscle

Another common mistake is to assume that running already provides all the muscle stimulus needed. Running places considerable demands on the legs, but that is not equivalent to the stimulus provided by strength training. 

The World Health Organization (WHO) recommends that adults perform muscle-strengthening activities involving the major muscle groups on at least two days a week.

For those who run with weight loss in mind, however, strength training does not need to compete with running. It can be precisely the complement needed, helping preserve strength and muscle mass while fat loss takes place.

Runners 40+: muscle is even more important

Turning 40 does not flip a switch that makes muscles disappear. But studies show that there is a progressive loss of muscle mass and function associated with aging (sarcopenia), a process influenced by factors such as physical activity, nutrition and health conditions.

At this stage, trying to lose weight through highly restrictive diets while increasing running volume can lead to a loss of lean mass. To help maintain or regain it, the international PROT-AGE group recommends at least 1.0 to 1.2 g/kg/day of protein for older adults

Read also: Muscle loss may begin after age 30, studies say

So, how can you balance your plate?

The amount needed depends on weight, age, goal, distance covered, training frequency and individual energy expenditure, but the logic remains the same: balance protein, carbohydrates and strength training, without drastic cuts.

A main meal can include a source of protein, such as lean beef, chicken, fish, eggs or plant-based alternatives, as well as a source of carbohydrates, vegetables and sources of fat, according to individual needs. Throughout the day, distributing protein-rich foods among different meals helps prevent practically all intake from being concentrated only at lunch or dinner.

On days with longer or more intense workouts, needs are not necessarily the same as on a rest day. Diet and training can be adjusted together.

In the end, for runners who want to lose weight, the scale is only one way to track progress. Preserving muscle, continuing to run well and maintaining enough energy to recover are also signs that the process is working.

And after 40, this change in perspective becomes even more relevant: instead of pursuing only a lower number on the scale, the goal can be to become lighter without giving up the strength that will help you continue running for decades to come.