weight loss

Losing Weight through Exercise Only – Fact or Myth?

Hey Angels and Alphas,

To lose weight and burn fat, you must consistently use more calories than you take in – everyone knows this. And typically, the best way to do this is to cut calories from your diet, add more low-energy-density foods into it, or add more exercise.

A lot of people don’t like the idea that they should rely on exercise at all. But losing weight and burning fat via exercise is possible, too – it just requires much more time and effort.


Recent research published inside the Medicine & Science in Sports & Exercise has suggested that you can lose through exercise alone. I mean, we all knew this already, but they did a great job at confirming it metrically.

The catch? You have to exercise a lot. In terms of numbers, we’re talking more than 300 minutes of exercise every week, which accounts to roughly 40 minutes a day.

I know what you’re thinking – that doesn’t seem like much at all. But we’re talking about high-intensity exercise in a heart rate range for weight loss… and that’s not as easy as it sounds.

Remember: The CDC recommends the minimum amount of physical activity for each week should be around 150 minutes. Here, we’re talking double that as a minimum.

Let’s dive a little bit deeper into the science of where that number came from and what it means for your weight loss success.

Here’s why it’s very difficult to lose weight through exercise only.

Any time you reach a calorie deficit, the foundation of fat loss, your body kicks in with a few compensatory mechanisms that are there to “balance the scales.”

One way your body achieves this is through slowing down your metabolism. This means you become more efficient at using calories, regardless of whether you’re at the gym or on the couch. This compensatory response is one of the reasons we’ve been able to survive famines and food shortages (not to mention running faster marathons.)

But if you’re trying to lose weight, compensatory mechanisms (such as a slow metabolism) become a massive roadblock.

On top of that, exercise also has a direct impact on the hormones regulating satiety and hunger. A control trial analysis done back in 2018 found that exercising for two weeks or longer is linked to a decrease in leptin, a hormone that prevents under and over-eating.

Exercise is also associated with increased acylated ghrelin in the body, a vital hormone for appetite control, as well as the decrease in insulin, a hormone that suppresses appetite. This all means you could be encouraged to eat even more.

And finally, exercise can also serve as a trigger for reward-driven eating behaviors. If you’re someone who likes to treat themselves after they finish a tough workout, you’re risking quickly chocking up the calories you just burned. Not to mention, you’re likely missing out on countless healthy and productive nutrients that could have made it to your post-workout snack.

Depending on the number of calories you burn via exercise, the cumulative effects of all the body’s compensatory mechanisms can bring your total calorie expenditure to null.

In fact, research in the past has found that these mechanisms compensate for a total of 1,000 calories daily in the lives of sedentary adults… regardless of how many calories they burn throughout the week.

This means if you’re burning 2,000 calories through exercise in one single week, all these compensatory mechanisms can quickly add up those calories back into your body without you even realizing it.

So… why exactly 300 minutes of exercise for weight loss?

Kyle D Flack, head researcher on the 300-minute study, found that 300 minutes is roughly how much exercise sedentary adults need to do if they want to out-run the body’s compensatory mechanisms.

To find that 300-minute number, he and his fellow researchers brought together 44 overweight, sedentary adults and put them into 3 groups. Then they tracked how many calories they’ve burned through exercise inside a 12-week period.

  • The first group was instructed to exercise anywhere between 40 and 60 minutes a day, six times a week.
  • The second group was told to exercise for about 90-120 minutes twice a week.
  • The third group performed no exercise.

All exercise groups performed aerobic activities at a minimum intensity of around 50-59% of their maximum heart rate. (To find your maximum heart rate, subtract your age from 220.)

The first group burned close to 500 calories per workout, for a weekly total of 3,000.

The second group burned about 750 calories per workout, for a weekly total of 1,500.

What researchers found is that both groups compensated about 1,000 calories. This means the first group burned 2,000 calories and compensated 1,000… still ending the week at a deficit of 2,000.

However, the second group achieved only a 500-calorie weekly deficit.

The result? The first group lost almost 4 pounds (of body fat) by the end of these 12 weeks.

Bringing it all together…

In an ideal scenario, you always want to be combining exercise and a healthy diet so you can achieve weight loss success.

And while you can still lose fat only through exercise, just be warned… it takes a lot to out-run your body’s natural compensatory responses. If you don’t want to go on a diet or keep eating junk for some reason, you need to expend at least 3,000 calories a week, or roughly 300 minutes of exercise, to see actual weight loss results. You will see progress, but it will be much, much slower.

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