We’ve been told as a society that exercising is one of the fastest and most effective ways to lose weight. The problem is that trying to lose weight with exercise can sometimes do more harm than good, according to a large-scale study of weight loss, workouts, and how they are connected.
The study tracked how much people ate and exercised and found that many of them failed to lose weight while exercising. Some of them even ended up gaining weight. This is because this big change had caused them to make other, subtler, changes – often without realizing it. Some of the people in the study did manage to lose weight though, and we can stand to learn something from their success.
If the universe was fair and balanced then exercising would, of course, lead to weight loss. Any kind of physical activity burns up calories. When calories are burned without being replaced or replenished, then we end up with a negative energy balance. That causes our body to burn up internal energy stores. Energy is stored in the body in the form of fat. So burning energy means burning fat which means losing weight.
Unfortunately, human metabolism is rarely so balanced or fair. Several studies have shown that people only lose up to 40% of the weight they technically should due to how many calories they burn through exercise.
Just why and how exercise can prevent weight loss instead of supporting it is still a bit of an unknown. Scientists looking into the issue believe that many people compensate for the calories they burn off by eating more or moving less – or both. Resting metabolic rates can also decline when people start losing weight. This will lead to another positive energy balance, which is when weight gain occurs.
It’s not clear whether people primarily overeat or move less as compensation for exercising. The answer to that question can be more important than it sounds. We have to know how we are compensating to stop doing it.
For this latest study, published in the American Journal of Clinical Nutrition, researchers at the Pennington Biomedical Research Center in Baton Rouge, Louisiana, worked with other institutions to get inactive people exercising so they could carefully track how their daily habits (not to mention their waistlines) changed over time.
The study began with the recruitment of 171 overweight sedentary men and women between the ages of 18 and 65. Their weight, typical hunger levels, metabolic rate, and aerobic fitness was measured, along with their daily food intake and energy expenditure. The researchers also used standardized psychological questionnaires to determine if participants felt that their healthy and good actions justified something less positive later down the line.
The researchers randomly assigned some people to continue living as a control, with others undertaking supervised exercise programs. One of these programs had people exercising on treadmills or exercise bikes three times a week until they burned eight calories per kilogram of body weight. That came to around 700 calories a week for the majority of them. The other exercise program had them burning 20 calories per kilogram of body weight, which came to an average of 1,760 calories.
These exercise routines both lasted for a total of six months. The volunteers wore activity monitors across the six months. Researchers regularly checked in on them; measuring energy intake, metabolic rates, and fitness. The volunteers were all left to eat whatever they wanted.
Everyone returned to the lab at the end of the six months for a comprehensive re-measurement. The numbers for the control group, including resting metabolic rate and weight, hadn’t changed much at all. The same also applied to most of the exercises though. Some of them had lost a bit of weight, but over two-thirds of people in the shorter-workout group and around 90% of the longer workout group lost less weight than expected.
The reason for that? They compensated for the extra calorie burn.
The scientists were able to determine that they hadn’t compensated by moving less though. The readouts for the activity monitors remained consistent. Rather, the exercisers were also eating more, according to the other calculations and measurements. The extra calorie intake was minor – only around 90 extra calories per day for the short-exercise group and 125 calories a day for the intense exercisers. Even so, that tiny amount was enough to undermine their weight loss.
An interesting takeaway from the study was that the people who compensated the most and therefore lost the least weight were the people who reported they believed making some healthy choices meant that they could make some unhealthy ones too.
They effectively felt that it was okay to swap their behaviors. They felt if they jogged now then they could have a doughnut later, for example.
This meant that they were losing very little if any, weight through exercise.
The study did also produce some more encouraging data though. The resting metabolic rate for just about all participants remained steady, which was good because a reduced metabolic rate would lead to more weight gain. The few exercisers who resisted the temptation to eat more did lose weight.
The difference between what the compensators and non-compensators ate was minimal. It was around 90 calories at best. Even so, that 90 calories had a significant effect on their weight loss efforts. Anyone who plans on losing weight through exercise should also keep a close eye on what they eat and resist the temptation to have a couple of extra bites.