How energy balance and flux affected future weight gain and obesity

You can pare your food down to the very bone all you want, but if you don’t pair it with physical activity, the pounds you shed will come back again and again. That’s why a joint team of South African and Oregon-based researchers suggested that obesity is best defeated through exercise rather than diet, according to an article from the U.S. National Institute of Health.

According to the two-nation research team, the current practice of limiting the caloric intake of obese people can be traced to the so-called "surfeit energy" theory. This theory proposes that excess energy intake turns into fat. Based on that theory, the best way to prevent fat is to reduce the amount of calories.

However, there are not many studies that tested the surfeit energy theory using objective estimates of how much energy an active human body takes in and expends. (Related: 10 Ways to Boost Your Metabolism Naturally.)

The researchers turned to a different theory. They believe the human body is better able to maintain its weight if there is a "high energy flux." That is, the body must be eating a lot of food while also expending a lot of energy in order to achieve stable homeostasis.

If that is true, then the reverse – a "low energy flux" with low caloric intake and low activity levels – would lead to a person gaining pounds instead of losing weight.

1. Study looked at adolescents and young adults
The researchers decided to look at how energy balance and flux affected future weight gain and obesity. They also wished to determine if their findings could be replicated in two separate samples.

To that end, they gathered two independent samples that were effectively independent studies. The first sample was comprised of 154 adolescents while the second sample consisted of 75 young adult females who were of the age to go to college.

The participants of both samples fasted for 10 to 12 hours before reporting to the laboratory. Their resting metabolic rate and percentage of body fat measures at baseline were recorded.

Each participant was given doubly labeled water, a type of water made out of easily-tracked isotopes of hydrogen and oxygen. Analyzing urine samples allowed researchers to take objective measurements of a participant’s total energy intake (TEE) and total energy expenditure (TEI).

All participants returned two weeks later. Once again, the researchers measured their resting metabolic rate, percentage of body fat, and TEE and TEI.

The researchers followed up on the adolescent participants on an annual basis for a total of three years. They did the same for the young adult sample, although it lasted for only two years.

2. Metabolic rate determines future body fat gains, not caloric intake
The researchers reported that low energy flux led to body fat increases in both the adolescent and the young adult samples during the follow-ups. This state was the result of minimal physical activity, which resulted in a low resting metabolic rate.

Furthermore, high energy flux was shown to prevent body fat gains in the future. The researchers determined this was because the increased amount of activity led to a higher resting metabolic rate.

Resting metabolic rate is the amount of energy the human body uses when it is at rest. Increasing physical activity has been shown to raise the rate at which the resting body metabolizes food.

In conclusion, the researchers believe that expending more energy could be more effective at reducing body fat and preventing it from returning than the currently-practiced method of caloric restriction. To achieve "high energy flux," obese people need to increase their level of physical activity, therefore boosting the rate they burn fat even at rest.