Let’s get one thing straight: exercise is not about “burning calories”. The amount of calories you actually burn exercising compared to sitting and doing nothing is not really that much. It certainly adds up very slowly when you consider that 3500 calories is equivalent to one pound of stored energy. If you want to lose weight, focus on your diet (see my post Tips and Tricks For Losing Weight). But, while diet changes will make the largest contribution to weight loss, it’s important not to ignore exercise! However, think of exercise as your hormone management, not your calorie burning.
Hormones are chemical messengers in contact with virtually every cell in your body, sensitive to the demands of your cells, sensing changes in your body’s chemistry, and responding rapidly to ensure that the cells in your body get everything they need to stay healthy. Exercise has a profound effect on every hormone system in your body. Whether that exercise is aerobic or anaerobic, cardio intensive or strength training, low-intensity or high-intensity, and short duration or long duration, changes how that exercise affects each hormone system. It also matters what time of day you exercise, whether or not you exercise in a fasted state, and what other stressors are present (mental stress, lack of sleep, poor quality diet, etc.). However, what is uniformly true is that exercise is beneficial to hormone regulation.
Some of the benefits of exercise are obvious. Increasing muscle mass causes an increase in metabolism, making it easier to maintain a healthy weight. Most people like the way they look better when they have bigger and more defined muscles (I do!). And it’s just plain handy to be stronger, faster, more flexible and more agile. But there are some additional benefits that you might not immediately think of as you contemplate adding more or different types of activity to your life. The field of exercise endocrinology (how exercise affects hormones) is enormous and I will be tackling many key areas in upcoming posts. In particular, I will touch on each of the following benefits to exercise:
Appetite and Weight Control: Exercise is known to regulate key hunger hormones such as leptin and ghrelin (I have a whole post on hunger hormones coming soon!) and may even promote healthier digestion through hormone regulation. It is not necessarily true that exercise makes you hungrier, although it may feel that way. In fact, for many people (and depending on the type of exercise), exercise makes it easier to naturally consume fewer calories in an entire day (even if you eat a bigger meal right after working out). Not only does exercise regulate your appetite, but many people find that they naturally crave more nutrient-dense foods. I myself crave fish and vegetables after an intense workout and while I feel famished, I actually fill up much more quickly than on days that I don’t exercise as much or as intensely. Exercise is also believed to help lower your bodyweight “set-point” (a controversial idea that basically says that there is a weight which your body “wants” to be, which is determined by your hormones, which are in turn influenced by diet and lifestyle).
Metabolism and Insulin Sensitivity: Exercise helps to improve insulin sensitivity through a direct action on the glucose transport molecules in the individual cells of your muscles. It also affects the full range of hormones related to accessing stored energy and regulating how that energy is used. This “boost” in metabolism is one reason why exercising can make you feel more energetic throughout the day.
Body Composition and Bone Health: When you exercise, your muscles get stronger (and sometimes bigger, depending on the exercise). This is one contributor to increased metabolism. And very importantly for long-term health, exercise (especially weight-bearing exercise) stimulates your body to make stronger and denser bones. Exercise or lack thereof is, in fact, a bigger determinant of osteoporosis risk than diet.
Stress Management: Exercise is very effective at modulating cortisol levels. This is a bit of a double-edged sword because exercising too intensely for your body can increase your cortisol level too high and lead to adrenal fatigue. However, if you keep exercise to a more appropriate duration and intensity for your fitness level (and appropriate for how well you eat, sleep and manage stress in other areas of your life), exercise becomes very potent at reducing and normalizing cortisol levels (which can also help reduce inflammation and promote healing). This makes it easier to burn stored energy (especially fat), improves your sleep, and makes you feel more relaxed and able to cope with life’s surprises.
Sleep Quality: Beyond its effect on cortisol, exercise regulates several key hormones related to circadian rhythms. This means that when you exercise during the day, you fall asleep easier, sleep more soundly, and experience more restorative sleep so you wake up feeling more refreshed (providing you allot adequate time for sleeping). Sleeping better positively affects just about everything in your body, from your cortisol levels to your body’s ability to heal and resolve inflammation. This is another double-edged sword because exercising too intensely too late in the day can make it more difficult to fall asleep.
Mood: Beyond its effect on the stress hormone cortisol, exercise releases endorphins which has a direct reflect on several key neurotransmitters that are related to mood. This means that making time to exercise can help fight depression and anxiety and improve your general outlook on life. Exercising also increases blood flow to the brain which can help reduce inflammation in the brain (which also has the net effect of boosting your mood), which is an important strategy for those with gut-brain axis problems.
What exercise is best? There are different benefits of exercise, depending on type, duration and intensity, but with the exception of over-training (exercising more too intensely or for too long of a duration for your body and current fitness level), all exercise is extremely beneficial. What exercise is best for you depends on your goals and your current health status. As I delve into the specific effects of different types of exercise on different hormone systems in upcoming posts, hopefully you will find enough information to guide your decision making when it comes to prioritizing one activity over another. But, what matters most is that you do something—even just a gentle stroll. And even better, do something you enjoy (for me, that’s yoga!). If you enjoy your activity, you are far more likely to keep doing it.