More than Calories In, Calories Out: Effects of Exercise
Sunday, November 14, 2010
LifeTime WeightLoss in Exercise, Fat Loss, Tom Nikkola, calorie balance

How many calories did you burn? What was your average heart rate? These are questions we often ask following an exercise session. They are easy measures of how hard we worked during a training session, but they don’t tell the whole story. As we continue this series More Than Just Calories In, Calories Out, today we’ll look at the metabolic effects of exercise. As you’ll see, exercise impacts our metabolism and ability to manage weight in more ways than just increasing the calories we burn each day. By structuring a proper exercise routine, you can help repair a dysfunctional metabolism or maximize a healthy one.

Exercise and Calorie Expenditure

For weight management, exercise is most frequently thought of as a means to increase total calories burned each day. The intensity of exercise performed is a major factor in how many calories an individual burns, but it also affects what type of calories are burned and in what way the body adapts after the workout. One unfortunate outcome of intense bouts of exercise in some people is that they may unknowingly compensate for what they’ve burned by either eating more during the day or by becoming more sedentary during the hours following the workout. This can be avoided by tracking nutrient intake and ensuring you maintain a normal level of activity. A study published in the Archives of Internal Medicines showed those who maintained 4 ½ hours of exercise each week were able to sustain a 10% decrease in body weight long-term. In the short-term, diet alone can produce weight loss, but the long-term success rate is minimal. Long-term weight management must incorporate diet and exercise together.

Exercise and Body Fat

I once had a very upset member approach me at the Fitness Services Desk. He had just walked out of the group fitness studio and I couldn’t tell whether his face was red from his workout or red from anger. He walked up to me and said (paraphrasing): “I am so frustrated with this place. I have been working my butt off in this cycling class for over a year. I go to cycling six days a week and I haven’t lost a pound. What’s wrong with your classes?” I paused for a moment, confused about his perception of the class being at fault. I tried to see it from his perspective and replied, “Wow, you’re really committed. I’m impressed you’ve stuck with it so long. There are a couple of issues that might be holding you back from shedding the weight. Could I set some time aside and talk with you about the types of workouts your doing and what your nutrition looks like?” Unfortunately, he wasn’t interested in changing anything. He didn’t want to do a different workout or change his nutrition. I saw him the next day with his cycling shorts and shoes on walking into the studio for another class. He just wanted to keep doing the same workouts and have them shed the fat. It doesn’t work that way.

Along with a proper nutrition plan, the right kind of exercise routine can help us shed body fat, especially the disastrous visceral fat, or belly fat. Higher-intensity exercise results in a better maintenance of lean body mass and a greater loss of visceral fat.(1,2) To maximize the effects of a workout program, it should include some of these higher-intensity days mixed in with lower-intensity days. Of course, strength training should be included on a regular basis.

Exercise and Stress Hormones

Stress hormones play a significant role in metabolism. Chronic stress raises cortisol levels, which increases the accumulation of visceral fat and can reduce metabolic rate by suppressing thyroid hormone. High-intensity interval training stimulates the release of cortisol and growth hormone.(3) The secretion of these hormones can be beneficial on occasion. However, those who are under chronic stress may find this type of training can be counter-productive to managing stress, and could lead to overtraining. Moderate to lower intensity training helps to lower cortisol levels.(4)

Exercise and Blood Sugar Management

Exercise affects how well the body handles the consumption of carbohydrate. First, it increases the ability of the muscles to store glycogen, the storage form of carbohydrate. Overall, the increase in the ability to store carbohydrates will not be significant as muscles typically only hold 250-400 grams of carbohydrate. Once glycogen stores are full, any additional available carbohydrate is stored as fat. A typical workout might use 40-150 grams of carbohydrate which can easily be replaced through a moderate-carb diet during the remainder of the day.

Exercise also has a positive effect on insulin sensitivity. Improved insulin sensitivity means the body can handle increased blood sugar levels with the production of less insulin. As people become insulin resistant, they produce greater amounts of insulin to deal with blood-sugar levels. Chronically high levels of insulin keep the body from burning fat, even in the case of a reduced calorie diet. It can also lead to a variety of other issues we don’t have space to discuss here. As insulin levels are kept lower by improving insulin sensitivity, the body is able to use more fat for fuel. Even though this benefit of exercise does not change the number of calories being burned, it changes the type that are burned – less carbohydrate is burned and more fat is used for fuel.

Exercise and Brain Chemistry

Our brains drive our behavior, so it makes sense that if we can optimize the functioning of our brain, it can have a positive effect on our health. According to Dr. Daniel Amen, in Change Your Brain, Change Your Life, exercise improves the ability to think clearly and improves planning abilities. By improving cognitive function, you may make better decisions about food, like not buying the muffin from the case at your favorite coffee shop. Amen also shows exercise enhances mood by increasing the utilization of L-tryptophan, an amino acid used for serotonin production. Balancing mood can be especially important for emotional eaters.

Additional benefits of regular exercise include its ability to fight depression, with studies showing it to be as effective, if not more effective, than depression medication in some people. It also combats anxiety and worry, which also drive poor food choices in some people.(5)

Exercise and Post-Exercise Calorie Expenditure

Following an exercise session, the body burns an increased number of calories. This is called excess post-exercise oxygen consumption (EPOC). The number of calories burned depends on the type of workout performed and the intensity of the workout. For those just beginning an exercise program, EPOC is minimal, as the exercise sessions are normally lower in intensity. Over time, as intensity levels increase, EPOC increases as well.(6) Although there is an increase in calories burned from EPOC, it is not a significant amount.

To maximize the effect of EPOC, workout intensities should be very high, but training sessions are usually short. Since the training sessions are usually short in duration, they tend to burn fewer calories during exercise, but a few more following exercise. Longer-duration, lower-intensity sessions burn more calories during exercise and fewer following it. Balancing the types of workouts you do in a systematic way can help ensure you gain the benefits of each of the types of exercise. In the end, EPOC will do little to increase overall calories burned, but what it does do is change what type of calories are burned. Following an intense training session, the body burns an increased amount of fat.


Commit to the time you spend exercising each week. If you’ve scheduled 45 minutes for a workout, during that time, workout. Do your workout with a plan and a purpose. You can get a very different outcome from your workout depending on your approach to your exercise session.

So often, people give up on their workouts because they don’t see results. Beyond changes in weight or leanness, results from exercise can be seen in how you feel, how you think, how you perform, how you sleep, etc. Pay attention to all the ways in which your exercise routine may be affecting you by keeping an exercise journal in writing or online. If you don’t have a plan, please, ask for help and follow the plan. If the plan you’re following isn’t working, don’t keep doing it in hopes things will change. Ask for help on how to change it.

Written by: Tom Nikkola, CSCS, CISSN


  1. Nicklas BJ, Wang X, You T, et al. Effect of exercise intensity on abdominal fat loss during calorie restriction in overweight and obese postmenopausal women: a randomized, controlled trial. Am J Clin Nutr. 2009;89:1043-1052
  2. Irving BA, Davis CK, Brock DW. Effect of exercise training intensity on abdominal visceral fat and body composition. Med Sci Sports Exerc. 2009;40(11):1863-1872
  3. Wahl P, Zinner C, Achtzehn S, Bloch W, Mester J. Effect of high- and low-intensity exercise and metabolic acidosis on levels of GH, IGF-1, IGFBP-3 and cortisol. Growth Horm IGF Res. 2010;20(5):380-5
  4. Hill EE, Zack E, Battaglini, et al. Exercise and circulating cortisol levels: The intensity threshold effect. J Endocrinol Invest. 2008;31:587-591
  5. Daniel Amen. Change Your Brain, Change Your Body. 2010. Harmony Books. New York, NY.
  6. LeCheminant JD, Jacobsen DJ, Bailey BW. Effects of Long-Term Aerobic Exercise on EPOC. Int J Sports Med. 2008;29(1):53-58

This article is not intended for the treatment or prevention of disease, nor as a substitute for medical treatment, nor as an alternative to medical advice. Use of recommendations in this and other articles is at the choice and risk of the reader.

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