Why can’t you solve a bad diet with exercise if you want to lose weight?

“If I kill myself in the gym, I can eat whatever I want” or “while I go for a run, I will have my weight under control.” Have you ever thought things like this? Do you think that watching the diet is secondary if you comply with the exercise?

We regret to tell you that you are in error. If you want to lose weight, you will have to be attentive to what you eat no matter how much you go to the gym practically every day. Unfortunately for everyone, when it comes to losing weight there are no shortcuts.

To lose weight you need a caloric deficit

To understand why it is not enough to exercise We have to start by explaining the most basic when it comes to losing weight: you need to achieve a caloric deficit. That is to say, that the kilocalories that enter are below those that are burned.

Our body gets the energy you need from food you consume, and when you consume more energy than you expend, it stores it in the form of fat tissue in anticipation of times of shortage, when you take in less than you need.


So if you want to lose weight you must get that your body draws on those fat reserves, eating fewer calories than you expend. All diets, both those that work long-term and those that are touted as miracle diets, are based on this principle. The difference is how this caloric deficit is achieved and how easy it is to avoid the yoyo effect or rebound effect (quickly recover everything lost).

Fast ingesting calories, slow in burning them

With the above in mind, you might think that you have enough to increase the amount of physical exercise What are you doing. So you would burn more calories and you could get that caloric deficit that will make you lose weight, right?

Well yes in theory, but in practice this is really difficult to achieve for the following reason: after thousands of years of evolution, most of it with a shortage of caloric foods within our reach, our body has developed a true talent to it is time to quickly detect, enjoy, and process calorie-dense foods and to slowly burn those same calories.

Eating a lot and moving a lot is more effective when it comes to losing weight than eating little and not exercising

From a purely technical point of view, our body is in that sense an enormously efficient machine. The problem is that in a world in which calories are no longer scarce, but we have plenty of them, that efficiency works against us, and it is difficult to maintain a healthy weight by focusing only on the part of physical exercise and neglecting food.

What you would have to run to burn these calories

The British Royal Society for Public Health published a table listing how much exercise it takes to burn certain unhealthy foods. We collect it here, translated into Spanish, to give you an idea of ​​the imbalance between calories that enter when eating and those that leave when exercising.

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Always keep in mind that there are more factors that influence the rate at which your body burns calories, such as the percentage of muscle mass or the physical state of each one. This is especially relevant in aerobic exercise, which the body ends up getting used to and every time you have to do more time of the same exercise to burn the same calories.

Unhealthy food

Approximate number of calories

Time to burn them walking at a good pace

Time to burn them running at a leisurely trot

Sugary soda


26 minutes

13 minutes

Standard chocolate bar


42 minutes

22 minutes

Vending machine sandwich (bacon and cheese)


1 hour and 22 minutes

42 minutes

A family pizza room


1 hour and 23 minutes

43 minutes

A medium coffee-shake


53 minutes

28 minutes

French fries or similar snack package


31 minutes

16 minutes

50 grams of roasted and seasoned peanuts


54 minutes

28 minutes

Sweetened industrial pastries


1 hour and 17 minutes

44 minutes

Bowl of breakfast cereals


31 minutes

16 minutes

Muffin pastries


48 minutes

25 minutes

What if you do other sports?

Maybe neither running nor walking is your thing. So how many calories do you spend doing your favorite sport? The Mayo Clinic published in October 2017 a compilation with this information, calculating the number of calories per sport putting as average subject a woman of 76 kilos and a man of 88.


Woman (76 kg)

Man (88 kg)

Ballroom dancing

219 calories / hour

273 calories / hour

Slow cycling (16 km/h)

256 calories / hour

319 calories / hour


314 calories / hour

391 calories / hour

Jogging on the elliptical

365 calories / hour

455 calories / hour

Swimming (moderate intensity)

423 calories / hour

501 calories / hour

Swim (high intensity)

715 calories / hour

892 calories / hour

rowing machine

438 calories / hour

546 calories / hour


584 calories / hour

728 calories / hour


584 calories / hour

728 calories / hour


438 calories / hour

546 calories / hour

Climbing stairs

657 calories / hour

819 calories / hour


752 calories / hour

937 calories / hour

Jump rope

861 calories / hour

1,074 calories / hour

Exercise without diet, bad solution

If you take a look at both tables you will see why try lose weight by relying exclusively on exercise without paying any attention to diet is not a great idea: if you are a woman, you need more than an hour of elliptical to make up a quarter of a pizza, and swim more than an hour at moderate intensity to burn a bun, and if you are a man, the numbers are a bit more on your side, but you are also more likely to have consumed larger servings.


In addition to not very effective, this way of approaching physical exercise can end taking away all the fun by turning it into a compensation mechanism, as a form of atone the guilt of what we eat. Similarly, unhealthy food can be seen as a reward we give ourselves after playing sports, paving the way for a possible eating disorder.

If we want to lose weight, it is better to diet, but if we want to maintain the lost, it is better to opt for sport according to the latest study

For effectiveness when it comes to losing weight and also as a way to enjoy the process much more, it is much more convenient to combined exercise and diet approach, understanding the diet not as a restrictive menu that tells you what you should eat at all times, but as a way to improve eating habits by reducing and eliminating ultra-processed foods, those with added sugars, those that are high in salt and those that use poor quality flours and fats.

By reducing these foods, we will reduce the calories we eat, especially those that do not provide us with beneficial nutrients, and combining it with exercise that caloric deficit that we talked about at the beginning occurs and that is, in fact, the only real method to burn fat.