Busting A Common Diet Myth
A common diet myth is that exercise alone will make you thin.
Now before we get into this one, I do want to mention that exercise has massive health benefits and you absolutely should try and get some regular exercise into your day.
Benefits include reduced blood pressure, reduced risk of Type 2 diabetes, stroke and heart attack. As well as lowering your risk of developing cognitive impairment from Alzheimer’s and dementia.
But, there is a common misconception that exercise alone will help you lose weight, and that’s just not true.
It’s actually pretty difficult to lose weight once you’ve gained it just by exercising more.
If you have lost weight, exercise can help with weight maintenance, along with watching your energy consumption.
One underappreciated fact about exercise? Even when you do work out, the extra calories that you burn only account for a very small proportion of your total daily energy expenditure.
Roughly 15-30%.
The 3 Main Components of Energy Expenditure
There are 3 main components of energy expenditure, by which I mean the energy you are using each day:
• Your basal metabolic rate (BMR). Which is the energy your body uses maintaining things such as your body temperature, keeping you breathing, keeping your heart beating, your kidneys filtering wastes etc.
• The thermic effect of food. Which is the amount of energy released, in heat, resulting from the consumption of food.
• The energy used in physical activity. Which is the voluntary movement of the skeletal muscles and support systems. And covers everything from taking out the garbage, and walking your dog as well as sport and overt exercise.
A fourth category, adaptive thermogenesis, is sometimes mentioned. This is the energy you use in order to adapt to dramatically changed circumstances, e.g. extreme cold, starvation, etc.
Your basal metabolic rate accounts for around 60-75% of your total energy expenditure. And digesting food about 10%. Adaptive thermogenesis is negligible, so it’s not usually counted.
This only leaves 15-30% for physical activity, of which exercise is only a subset.
Whereas your food intake accounts for 100% of your energy intake.
Exercise Can Actually Sabotage Your Weight Loss Efforts
Also, exercise can actually sabotage your weight loss efforts in other, subtle ways. When you exercise, you get hungry. And sometimes you get so hungry, you end up eating more calories than you burned off.
A 2009 study showed that most people increase their food intake after exercise, either due to being hungry or because they thought they’d burned off more calories than they actually had.
Even just one slice of pizza can undo the calories you burned during an hour’s gym workout. And who stops at one slice? I know I don’t.
The same goes for a muffin, café mocha or an ice cream cone.
People Often Move Less After Working Out
There is also evidence to suggest that people often slow down after a workout.
And so, they don’t move as much the rest of the day. You might go for a nap, or choose the elevator over the stairs because you’re feeling tired. Or virtuous cos ‘hey I had a workout today.’
These are called compensatory behaviours and are often made unconsciously, but they do tend to offset the calories you’ve burned.
There Is An Upper Limit To The Number Of Calories You Can Burn During Exercise
Other studies have shown that we may have an upper limit to how many calories our body is willing to give up when we exercise. We may have an upper limit so to speak. A point past which no matter how many hours you are spending in the gym, you don’t actually burn any additional calories.
Possibly the remnant from your ancient ancestors, a survival mechanism your body uses to conserve energy and hang onto stored fat for future energy needs.
Experts tell us that a lack of exercise and eating too many calories are the cause of weight gain. And they might be right.
But they cannot be seen as being equal contributors.
The Biggest Loser
You may have seen the show The Biggest Loser, a reality show in which overweight or obese contestants compete to win a cash prize by losing the most weight.
A study was done of the contestants in the 2009 show and they were followed up again 6 years later in 2015. All of the contestants lost huge amounts of weight, both due to extreme diets and hours and hours of exercise.
The Biggest Loser study found that those who lost the most weight on the show were not the ones who exercised the most, but rather those who ate the least.
You simply cannot outrun a bad diet. It’s too much food that’s making you fat.
So What Should You Be Doing?
The most important thing is to limit the amount of food, ie the calories or energy you are consuming, but without going hungry. Eat healthily, and focus on getting a bit of movement into your day.
But if you exercise obsessively without changing your eating habits, you are not going to lose weight. Or if you do, it’s going to be very very slow going.
And that is why it’s a myth that exercise alone will make you thin.
Sure exercise is fabulous for your health. And you should be getting some regularly for the numerous health benefits.
But it simply isn’t sufficient on its own for significant weight loss.
Last updated: 17/07/2022
