If you ask the average person why they’re exercising, they might tell you to lose weight. No doubt, exercise is a calorie burner and a sweat-inducing workout is an important part of any long-term plan to shed fat. Yet, exercising MORE isn’t necessarily better. In fact, beyond a certain point, additional exercise may NOT lead to further weight loss. This is especially true for aerobic training like walking or running.
If you burn more calories, you theoretically should lose weight, assuming you keep your calorie intake the same. Unfortunately, studies show we have a tendency to eat more when we exercise more. Have you ever heard a little voice inside telling you it’s okay to have a cookie because you worked so hard? It seems like that little voice speaks to lots of people. Plus, there’s the issue of how exercise affects appetite.
Exercise, Appetite, and Calorie Consumption
Even though some studies show exercise curbs appetite, the reduction in hunger doesn’t seem to reduce calorie consumption overall. In one study published in the Journal of Sports Medicine and Physical Fitness, researchers asked participants to estimate the number of calories they burned working out and then consume roughly that amount. As it turns out, we’re not very good at estimating how many calories we expend during a workout. The participants ate 2 to 3 times the amount that they actually burned.
Overestimating calorie burn and feeling a bit entitled for working so hard are two reasons why exercising a lot doesn’t lead to weight loss – but those aren’t the only ones. Another study found that people who did moderate amounts of physical activity burned about 200 more calories daily relative to inactive folks, but those who did the MOST exercise burned about the same number of additional calories as those who exercised moderately. How can that be?
Adaptation to Exercise
Numerous studies show that your body adapts to physical activity, especially doing the same exercise over and over again. That’s not hard to believe, is it? Your body adapts to whatever stress you place on it. That’s why it changes and also why it STOPS changing. When you do long workouts, your body sees those grueling workouts as a threat to homeostasis and fights it. Your body wants to make sure you always have enough energy reserves.
If you’re spending 90 minutes a day working out, you become more efficient at doing those movements. The goal of your body is to expend the least amount of energy possible doing the activities you ask it to do. You may not notice it but you become more efficient at doing those movements and you’re burning fewer calories as a result. If you think about it, you probably plan your activities to conserve energy as well. If you have items to take downstairs, you take them all in one big stack rather than making three or four separate trips.
The Stress Response to Too Much Exercise
Doing a high volume of exercise can also trigger your body’s stress response. Your body adapts to working out, which is a stressor, by adjusting in a way to better deal with that stress. After it adapts, you won’t make further gains unless you INCREASE the stress on your body. That’s why you need to ramp up the intensity or change one or more training variables to stress your body differently to continue to see change.
On the other hand, if you do TOO high of a volume, you can exhaust your body’s ability to adapt. At this point, metabolic changes take place, such as an increase in cortisol. The release of cortisol breaks down muscle tissue and does other undesirable things like suppresses your immune system. High cortisol also makes it difficult to sleep, and more. So, you have to find the “sweet spot,” the amount of exercise that challenges your body enough to keep it adapting but not so much that it exhausts it. Doing excessive amounts of cardiovascular exercise can do this. You can also over-train with weights by training too often, maxing out every session, and by not giving your body enough time to recover between workouts.
Too many people have the mindset that more exercise is better for weight loss. Since they’re burning more calories, they reason, they WILL lose weight. However, they don’t consider factors like the effect training has on appetite, eating habits, the stress response, and the tendency of their body to adapt and become more efficient doing the same movements. So, what do these folks do when they don’t lose weight? They increase their cardio even more. It becomes a vicious cycle that leads to stress, exhaustion, and, often, little or no weight loss. Even worse, excessive exercise can lead to muscle loss because your muscle is producing more cortisol.
Cut Back and Restructure Your Exercise Plan
You need some cardiovascular exercise but you can get the benefits from 30 minutes or less a day or every other day. If you do high-intensity exercise, you can get by with even less physical activity – 20 minutes or so of high-intensity interval training. Your body is less likely to adapt to this type of exercise since you’re pushing your body to near-max during the active intervals and keeping the sessions short. Most studies show that high-intensity exercise is more effective for fat loss than moderate-intensity exercise. Plus, you get the benefits of a greater afterburn with vigorous exercise.
For best results, combine HIIT training with weight training. If your body is accustomed to doing mostly cardio, the change will often “shock” your body into fat loss. Devote at least as much, if not more, time to weight training as you do cardio. Building muscle will give you more metabolically active tissue and increase your resting metabolism, whereas excessive amounts of cardio have the opposite effect. Just as importantly, give your body sufficient time to rest. Add a twice-weekly yoga session to your routine to counter the cortisol effect and help you relax.
Finally, keep an exercise and food journal. Overeating in response to training and under-fueling can both cause your body to hang onto fat. If you’re restricting calories and carbs too much, it can further promote a rise in cortisol. It’s important to know how much you’re eating, especially if you’re not losing weight.
The Bottom Line
Now you know why too much exercise, especially cardio, doesn’t always lead to the expected amount of weight loss and, in fact, can lead to a vicious cycle of stress and changes in body composition. Just as you can impede weight loss by cutting your calories too low, you can’t stall it by exercising too much. Don’t let this happen to you.
J Sports Med Phys Fitness. 2010 Dec;50(4):377-84.
Science Daily. “There May Be an Exercise ‘Sweet Spot’ for Losing Weight”
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