According to science, how do we understand about the role of physical exercise in losing weight?

Body weight loss is always a concern to those who love bodybuilding. Socrates (470/469 BC – 399 BC), a Greek philosopher and the founder of Western philosophy, used to say: “No man has the right to be an amateur in the matter of physical training. It is a shame for a man to grow old without seeing the beauty and strength of which his body is capable.” And then we hit the gym every day with the hope that we will see the result someday. However, humans are still confounded why some people can lose weight and build body, but some cannot, or at least it’s so difficult for them. Until more than two thousand years later, there’s Science!

No matter how much exercise, our body changes to use the same amount of energy every day.

Herman Pontzer, an anthropologist at Hunter College, set out on a journey to Tanzania to study the Energy Expenditure of the Hadza people. Hadzas are the hunter-gathers that still rarely exist nowadays because of the developing technology and industry.

Hadza people are ideally hunter-gathers. It is quite logical to choose them as subjects for the study, which is to measure the Energy Expenditure of hunter-gathers and compare it to that of modernized humans today. Hadza men are hunters that hunt animals with their own built bows and arrows; on the other hand, women are multitasking, carrying infants on the back and gathering edible food. Children also help transporting water buckets back to camp. In the afternoon, they come back and gather around a small campfire to talk and share. This is a typical day in Hadza population.

Hadza people
Hadza people near Lake Eyasi, Tanzania

Pontzer and his colleagues used a method called Doubly Labeled Water (DLW) to measure the Energy Expenditure of Hadza people on a daily basis.

What they found out was so intriguing: statistically, Hadza men burned approximately the same of the amount of calories (about 2600 cal) as the adults in the U.S. The same goes with Hadza women (about 1900 cal).

Conclusion: our bodies adapts to the change of the levels of physical activity to make sure that it uses the same amount of calories every day to maintain itself. 

Our biological evolution

Human beings have evolved and changed their behaviors and make-up so that the energy expenditure can be conserved. For examples, with a higher level of physical activity, your body tends to decrease energy for the production of estrogen. Some people also subconsciously like to sit rather than to stand for energy conservation.

So why exercise does not aid much in losing weight?

It we have a body that is stable, our body uses one-thirds of energy for physical activity. On the other hand, the other left two-thirds are utilized for body maintenance at rest (also called the Base Metabolic Rate aka. BMR).

Our body evolves to store more energy under the pressure of evolution (survival sake). Suppose if a person loses some weight, their BMR will decrease and the body also will become smaller. Now the body has been stabilized at a new, lower level of energy, so it has to maintain the new level against the evolutionary force of storing energy.

That’s when scientists indeed argue that exercise can help weight maintenance by helping the body lose energy in different ways (for example heat loss). For example, if a man needs an average of energy of 2600 cal for a living day and he’s had a stable body weight. Any exercise will help him get rid of any extra or excessive energy our of the body.

The Energy Equation

What can we do?

Because exercise only focuses on one-thirds of the total energy. We need to come up with different plans to cope up with the other two-thirds.

Energy comes from different food

There are three major sources of energy: fats, carbohydrates (sugar), and proteins. The bodies extract a different amount of calories from each type: 4 calories of energy per gram from proteins and carbohydrates and 9 calories per gram from fat (aka. Atwater factors). A healthy diet makes a healthy man.

How our brain perceives of types of food.

One technique usually used to counter eating desire is to prevent any hunger feeling in case of the adequate intake of energy. Food that is high in protein and fiber and low in carbohydrates (do not cause a sudden increase in calories) helps suppressing the hunger. For instance, salmon is especially high in protein and does not contain carbohydrates. Besides, the body will expend much more energy (in chemistry, it is activation energy) to digest protein than carbohydrates and fats, which helps avoid storing any extra calories.

We determine how much energy we need

The base metabolic rate will change depending on each individuality. It changes over ages, genders, and the make-ups of the body. For example, older people need less energy to maintain their body than they did in youth. Males tend to use more energy than women (considering some calories stored for the muscles strength).


After all, we cannot go against our evolution. Before humans become what they are today, they had to fight for their survival so that they could take over the planet. It is the mechanism in our bodies that keep us conserve energy and ensure our survival.

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References:

Susan,B. Roberts & Sai, Krupa Das. “The Messy Truth About Weight Loss”. Scientific American June. 2017: 36-41.

Herman, Pontzer. “The Exercise Paradox”. Scientific American Feb. 2017: 26-31.

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