Weight Gain with Exercise – Causes and Ways to Overcome It

Regular exercise is one of the proven methods for losing weight alongside calorie restriction and other dietary changes. In the face of the obesity epidemic in recent decades, exercise should not be seen as optional for weight management but rather as a mandatory strategy to lose weight. Health authorities advise 120 to 150 minutes of exercise a week, divided into 30 minute sessions over 4 to 5 days per week.

Why does exercise cause weight loss?

It is important to first understand how exercise leads to weight loss. The body requires energy for all its physiologic processes, even at rest.  A more active a person is, the more energy the body needs. This energy utilization can be measured in calories and is acquired from food. The more you eat, the more calories are stored as fat if it is not ‘burned’ with exercise. Similarly, the less you exercise, the more unused calories are stored as fat. This leads to weight gain.

However, many people who start with an exercise program may experience weight gain within the first week or even month. This seems contradictory to the weight loss benefits of exercise. It often confuses and even frustrates people who are committed to losing weight and start an exercise program for this purpose. There are physiological reasons why this initial weight gain occurs and it is important to understand that it is only temporary.

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The two main reasons for weight gain with exercise is water retention and muscle mass. An increase in both occurs with exercise and is a normal part of becoming more physically active. The changes that lead to increased water retention are temporary. Increase in muscle mass is permanent as long as exercise is continous but this will help the body ‘burn’ fat and reduce fat storage which in turn leads to weight loss over time.

Another factor that will also lead to some weight gain over time is an increase in bone mass density. Bones strengthen with physical activity and this can contribute to some increase in body weight over a prolonged period of time.

Water Retention with Exercise

Approximately 70% of the human body is composed of water. Changes in the water volume directly impacts on body weight. With exercise there is micro-tears in the muscles which results in inflammation that lasts for 1 to 2 days. This is known as delayed onset muscle soreness. As a result of this inflammation, the body triggers temporary water retention which leads to mild to moderate weight gain.

Furthermore, the muscles need to adapt to the increased workload with exercise by ensuring that there is a suffcient energy supply. Glycogen is a storage form of glucose that can be converted and utilized as an energy supply for muscles. The muscles attempt to store more glycogen initially and this requires water since glycogen is bound to water. Therefore this additional glycogen storage may cause minor water retention in the short term.

Muscle Mass with Exercise

A more widely known reason for weight gain with exercise lies with the increase in muscle mass. The body increases muscle cells with repeated exercise of different muscle groups. This causes an increase in the muscle mass. Overall muscle weighs more than fat with regards to the same volume of muscle and fat. Therefore a person may not necessarily notice a larger muscle bulk initially but the weight gain is detectable.

Despite the initial weight gain, this increase in muscle mass and therefore weight is positive. Eventually the fat stores are reduced and there is weight loss as well as a reduction in body fat percentage. Muscles are high consumers of energy even when at rest. A higher muscle mass means that more fat will be burned and less unused calories will be deposited as fat since the muscle cells utilize this energy for its needs.

Read more on ways to speed up metabolism.

How To Overcome Exercise-Related Weight Gain

By reducing dietary calories and increasing activity calories, weight loss will occur over time. Usually the focus is more on reducing body fat percentage, however, most people focus instead on body weight. The initial weight gain with exercise should not be a cause for concern as it is temporary, lasting for a few days to a month. Therefore there is no need to take specific measures to counteract or reverse this weight gain and it will resolve in time.

Continue Exercising

Do not stop exercising due to this initial weight gain and do not allow it to demotivate you. It is temporary and the excess weight will be lost in a short period of time. Often it will be accompanied by further weight loss beyond the original body weight at the time of starting exercise. Ensure that you exercise regularly for the maximum benefit. It is also important to do both cardiovascular exercise and weight training as part of a workout regimen.

Reduce Dietary Calories

Every weight loss program should include both dietary changes and physical activity. While one on its own will also lead to weight loss if done properly, a combination of calorie reduction in food accompanied by exercise will lead to quicker and more consistent weight loss. However, do not starve yourself as this can further promote weight gain. Adults can safely reduce calorie intake to about 1,800 calories per day but it is advisable to consult with a dietitian.

Maintain Adequate Water Intake

Exercising means that your body will be utilizing more water and electrolytes. This has to be constantly replenished by drinking sufficient water, eating well (but not excessive calories) and using oral rehydrating solutions (ORS). Rehydration is crucial to prevent cramps, headaches, strain on the heart and kidneys. The mild water retention will pass with time.

Avoid Diuretics

Diuretics are substances that cause the body to lose water in the form of urine. These substances include pharmaceutical drugs as well as alcohol and caffeine. The drugs should never be used unless medically required for conditions like hypertension or heart failure.  Minimize alcohol and caffeine intake while ensuring sufficient rehydration.


It is always advisable to have a medical assessment before starting an exercise program. Sometimes the weight gain with water retention could be a sign of a strained heart due to exercise. This may also lead to visible signs like swelling of the legs. Medical attention is therefore necessary and this weight gain should not be ignored.

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