Weight Loss

Can you lose weight with exercise alone? Here's the science.

April 18, 2024

Written by Chandana (Chandy) Balasubramanian

Medically reviewed by

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Key Points

  • Studies show you cannot lose weight through exercise alone
  • Weight loss is complex, and many factors make it hard to lose weight
  • What you eat is most important for weight loss
  • Consider a registered dietitian for a personalized plan for sustained weight loss

If you started an exercise program to lose weight, you are not alone. And if you’re disappointed by the numbers on the scale after all the working out, you’re still in good company. 

Unfortunately, while the eat-what-you-want-and-work-it-off concept is seductive, it does not work. Research shows that we burn only very little of what we eat through exercise.

Exercise is vital for health, just not weight loss

If you get on a treadmill, visit your spin class, or hit the gym regularly, keep going. Exercise offers us immense benefits. It improves heart health, strengthens lungs, makes our bones and muscles stronger, and reduces the risk of diabetes, cancer, and other chronic conditions. 

It also boosts our mental health. Movement helps us manage symptoms of depression, increases focus, and helps us live longer.

However, if the main reason you exercise is to lose weight, you may need to readjust your expectations. Weight loss is a complex process, and the calories-in, calories-out approach to diet and exercise is a myth.

Exercise burns only 10-30% of our daily calories

The body does not work like a bank – we do not deposit calories through food, only to withdraw the same amount later through exercise. 

This philosophy has been quite popular for decades because of aggressive marketing by fast-food companies and the fitness industry. Instead, our body balances our weight carefully, based on its needs.

Here’s how our body uses our energy:

  • 50-80% of energy: Most of the calories we eat are used to keep our lungs and hearts working, balance hormones, and perform other basic functions. This is called the Basal Metabolic Rate (BMR), and it represents the energy we burn at rest. Our BMR uses 50-80 percent of our daily energy just to keep us alive.
  • 5-10% of energy: Another 5-10 percent of our energy manages our digestion, absorbing and transporting nutrients, and much more.
  • 10-30% of energy: Only about 10-30 percent is left for all our physical activity, the majority of which involves basic movements (think turning your head, blinking, fidgeting, changing positions, and lifting your hands).

Our bodies tend to resist weight loss

Our bodies use most of our energy for basic metabolic activities. The amount of calories we burn is directly related to our weight. If we weigh more, it takes more energy to move or perform basic functions, even when our body is at rest. This means our metabolism decreases as we gain weight.

Additionally, once we lose weight, our bodies actively try to gain it back. This is because the body works like a thermostat and tries to maintain a stable weight range. If we do not make long-term dietary changes, it may be harder to keep the weight off. This process is also the reason why fad diets do not work.

If you would like to talk to someone about achieving sustained weight loss, consider a Registered Dietitian for a personalized nutrition plan. Fay can help you find a Registered Dietitian near you, covered by your insurance.

You may feel more hungry after working out

Studies show that you get more hungry after longer moderate exercise than shorter bursts of high-intensity workouts. This may be because exercise suppresses ghrelin, the hormone that regulates hunger, but only for a short period of time. After about an hour, you may feel ravenous and eat more.

There’s also a psychological reason why you may eat more after exercising. Many people reward themselves for working out by indulging in more calorie-dense or processed foods. But research shows that the extra slice of pizza or a bigger portion size can outdo any benefits you gain from exercise. 

So, your diet is the most critical factor affecting weight loss.

Stress can make you gain weight

When we are stressed, our bodies release a hormone called cortisol. Cortisol and other stress hormones prepare us to fight, flee, or freeze (hide) from an immediate threat. During this time, these hormones slow down processes that are not needed and accelerate others.

Our stress hormones raise our blood pressure and trigger insulin release. Large insulin spikes make our blood sugar crash, which triggers cravings for foods high in carbs, sugar, and fat to give us an instant boost.

Unfortunately, in the long term, stress can make us gain belly fat and slow our metabolism down. This makes it hard to sustain weight loss efforts, even if you are physically active.

Bottomline: The right diet is most important for weight loss

Many factors affect weight loss, including what you eat, how you feel, and how your body processes your nutritional needs. For example, you may experience weight gain if you add too much fiber to your diet too fast. If you have insulin resistance, insulin spikes can lead to intense food cravings, leading you to eat more.

If you are obese or have belly fat, your body may slow your metabolism and prevent you from losing weight. For some, an imbalance of gut bacteria can override feelings of fullness after eating, causing overeating.

Mental health conditions can complicate matters further. If eating is followed by feelings of shame, disgust, or guilt, it could lead to binge eating or other types of disordered eating.

You don’t have to manage your weight or food intake alone; a Registered Dietitian may be able to help. Use Fay to schedule an appointment with a Registered Dietitian near you, covered by your insurance.

The views expressed by authors and contributors of such content are not endorsed or approved by Fay and are intended for informational purposes only. The content is reviewed by Fay only to confirm educational value and audience interest. You are encouraged to discuss any questions that you may have about your health with a healthcare provider.


Fay Nutrition has strict sourcing guidelines and relies on peer-reviewed studies, academic research institutions, and medical associations. We avoid using tertiary references.

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Chandana (Chandy) Balasubramanian

Written by Chandana (Chandy) Balasubramanian

Chandana Balasubramanian is an experienced healthcare executive who writes on the intersection of healthcare and technology. She is the President of Global Insight Advisory Network and has a Master’s degree in Biomedical Engineering from the University of Wisconsin-Madison, USA.


Medically Reviewed by