Sports Coach Logo Sports Coach Training Principles Fitness Components



text Translator



site search facility





Exercise and low carbohydrate diets make poor partners

Charles Remington explains the problems you may experience when you mix exercise and a low carbohydrate diet in an attempt to lose fat without losing muscle.

Over the last twenty-five years, the most common questioned asked me by frustrated exercisers, has been what exercise routine will get me the body I desire? My answer is always the same. They need to start exercising better judgement and learn that exercise alone will not solve their body composition problem. I believe the number one reason for starting an exercise program is weight reduction, even before fitness and health concerns. Exercise by itself is a poor weight manager, and it increases the need for better nutritional requirements. I believe I would receive minimal disagreement that a combination of nutrition and exercise is the answer to improvement in weight loss (fat loss), fitness and health risk concerns. With obesity reaching epidemic rates and the dropout rate of most health clubs' remaining high, this article intent is to lay the foundation of why exercise and low carbohydrate diets are poor partners.

The quest for the ideal body

Over the last three decades, I have seen extreme changes in the macronutrients (proteins, carbohydrates and fats) combinations in our quests for the ideal body. Everything from high carbohydrate, low fat, high protein, to the current low carbohydrate craze has bombarded us, though the failure rates in managing our weight continue to rise. The problem lies in our body's ability to adapt to change, especially extreme change. If your goal is to lose fat, you must provide your muscle with enough quality fuel without being over fuelled. This is especially true if your goal to lose fat includes exercise. The secret is not found in the elimination of macronutrients, but the management of them. Understanding how to fuel your muscles before exercise sessions and replacing fuel after workouts is critical or your body will break down muscle for fuel.

Fuel for muscles

Understanding how our muscles use the calories we eat as the fuel for muscle contraction is the first step in knowing what to do and not to do. Basic nutritional knowledge tells us that proteins repair and rebuild cells, carbohydrates energize cells, and fats provide the hormonal foundation for cells. When we lack balance in protein, carbohydrates and fats are bodies adjust and can use all three as a source of fuel for muscle contraction and cellular energy.

ATP Production

Though energy is needed for all cellular function, the focus of this article is muscle contraction and body composition. All muscle contraction derives energy from adenosine triphosphate or ATP. The primary source of ATP comes from glucose, which is stored in the muscles and liver as glycogen (glucose and water).

Muscle contraction during anaerobic activity (resistance training) can use glycogen directly to form ATP. The process is anaerobic glycolysis, meaning it can use the glucose as energy with very little oxygen (90% glucose, 5% oxygen and 5% fatty acid). Our muscles only store enough ATP for short periods of muscle contraction when depleted leads to muscle failure. The rest period between weight training sets allows additional ATP to be produced.

During the early stages of aerobic exercise, ATP is again created primarily from glucose until the heart and lungs provide enough oxygen to the muscles to allow fatty acids to be used to create ATP. So, there you have it during resistance training and the beginning stages of aerobic training, the primary source of fuel is glucose. This supports my claim that low carbohydrate diets and exercise make poor partners. To uncover why we need to quickly look at the concept behind low carbohydrate diets and how they work.

Low carbohydrate diets

Any diet that provides 100 grams or less of carbohydrate daily will quickly deplete the glycogen stores in the muscle and liver. This by itself is a testimony that our muscle's primary source of fuel is glucose. Fatty acids stored in the adipose tissue (fat cells) are now released into the blood and processed by the liver. Some are turned into glucose (gluconeogenesis), and some remain fatty acids and both provide ATP for muscle contraction. One of the by-products of this process is the ketone bodies which can provide energy to the brain and nervous system. The problem of gluconeogenesis (non-glucose turned into glucose) provides fuel to the muscle less efficiently than glycogenesis (glucose). The result is increased muscle fatigue, decreased muscle power, which leads to poor athletic performance.

Low Carbohydrate study

A recent study performed at the University of Connecticut showed that exercisers who switched from a balanced diet (proteins, carbohydrates and fats) to a low carbohydrate diet experience the following drops in athletic performance. There was a 7 to 9% drop in muscle power and a 6% drop in the VO2 max of cardiovascular performance. Another factor to consider is the recovery of muscle between workouts is decreased on low carbohydrate diets.

So why would someone go on a low carbohydrate diet, especially when exercising?

Because the initial weight loss that comes from glycogen depletion is believed to be fat loss. We have become so focused on weight loss, that any weight loss is seen as useful. As identified earlier in this article, glycogen is a mixture of glucose and water, and the majority are stored where? You guessed it, the muscle. A large percentage of the initial weight loss is coming from muscle loss. I do not think any exerciser desires to have smaller muscles as a result of their exercising. The goal of exercise should be to improve body composition, the percentage or ratio of muscle to body fat. This can only be accomplished by losing fat without the loss of muscle tissue. Maintaining muscle mass is vital to sustainable weight control. The following steps will protect your muscles as your losing fat while reaching your ideal weight and ideal body composition.

1. Cycle fat burning days with recovery days.

The secret to losing fat without losing muscle starts with not being too aggressive or extreme with your reduction of carbohydrates. You need carbohydrate management, not carbohydrate elimination. Over the last 12 years, with more than 10,000 clients I have found by reducing carbohydrates by 20% of daily needs and within 48 hours replenishing the glycogen in the muscle by eating 100% of daily carbohydrate requirements, allows for fat loss, without muscle loss. You have two fat burning days, then a recovery day. By doing this, you will have the best of both worlds. You will experience a fat loss that averages between 1 to 2 pounds weekly, while muscles are being well fed. You never drastically deplete the glycogen stores in the muscle, so athletic performance is not affected like on a low carbohydrate diet.

2. Exercise on days where you are receiving more carbohydrates.

Exercising on days where muscles are getting more carbohydrates for fuel and taking days off from exercise when you are aggressive about fat loss. One of the most difficult thoughts for exercisers to accept is that most of the results from exercise come when we are not exercising. They come after we exercise and in direct response to how the muscles receive nutrition after exercise.

3. Exercise 1½ to 2 hours after eating when blood sugar levels and insulin levels are slowly declining.

As insulin levels increase in response to a rise in blood sugar after a meal, the cells are in an anabolic state (receiving nutrients). Insulin is the hormone that feeds are cells. As blood sugar levels drop, insulin levels drop, and the pancreas produces the hormone glycogen and nutrients stored in the fat cells are released to the blood and used for energy. The management of this blood sugar rise and drop is important. If blood sugar levels go too high insulin feeds the muscle cells and deposits excess into fat cells. If insulin levels go too low, the muscle cells are being underfed. A slow rise in blood sugar provides good nutrition to the muscles, and a slow drop allows glycogen to take from the fat cells. Timing your exercise to this blood sugar decline allows the muscles to receive from the fat cells more effectively. It is vital to never exercise without having at least one meal left in your day so that muscles can recuperate from exercise.

Final Thoughts

Long-term success in managing weight starts with the right approach. If you are overweight, the real problem is that you have too much body fat for how much muscle you possess. A body composition solution is needed, not just a weight loss diet. Your goal should be to lose fat without losing muscle or sacrificing your health in the process. To maintain your results, your eating habits must develop lifelong character. Low carbohydrate diets provide initial weight loss, but at the high cost of losing muscle and reducing metabolism. They are inadequate sources of fuel to support exercise activity, which is vital in maintaining good health. The risks to your health long term make low carbohydrate diet's poor solutions for lifelong weight management.

Article Reference

This article first appeared in:

  • REMINGTON, C. (2004) Exercise and low carbohydrate diets make poor partner. Brian Mackenzie's Successful Coaching, (ISSN 1745-7513/ 18 / December), p. 4-6

Page Reference

If you quote information from this page in your work, then the reference for this page is:

  • REMINGTON, C. (2004) Exercise and low carbohydrate diets make poor partner [WWW] Available from: [Accessed

About the Author

Charles Remington is a Nutritionist from Connecticut, U.S.A. and in 1992 discovered a way to influence hormonal change so our bodies would lose fat without losing muscle or reducing metabolism.