This is an excerpt from Fundamentals of Sport and Exercise Nutrition by Marie Dunford.
Body fat is reduced when there is a caloric deficit over time. The fundamental principle remains the same regardless of the specific program followed—eat less, exercise more, or do both. As a rule of thumb, 1 pound (0.5 kg) of body fat contains about 3,500 kcal. Mathematically, if a person reduced food intake and increased exercise by a combined 500 kcal daily, then in seven days' time he or she would lose 1 pound of body fat. Such estimates are correct, but a 500 kcal deficit is very difficult to achieve for most sedentary people, many recreational athletes, and many small-bodied athletes whose caloric intake is relatively low. Losing substantial amounts of body fat takes time and sustained motivation.
There is no shortage of advice on the subject of weight loss, but when applied to athletes there are some important issues to consider. The most important are timing, degree of calorie restriction, composition of the diet, and avoiding strategies that will undermine training, recovery, and performance. Athletes need to understand the following:
- Weight loss is not necessarily fat loss.
- Rapid weight loss is usually a result of water and glycogen loss as well as some muscle, which can hamper training, performance, recovery, and health.
- A realistic expectation is the loss of 1 to 2 pounds (0.5 to 1 kg) of body fat per week. A 20-pound (9 kg) loss can take two and a half to five months, so athletes must plan accordingly.
- The best time for most athletes to lose body fat is in the off-season or early in the preseason.
- Restricting calories during periods of rigorous training or competition may hamper training, recovery, or performance.
- Daily caloric intake should be less than usual, but too great a restriction will likely result in too low of a carbohydrate intake to support training and recovery.
- Adequate protein intake and resistance exercise help to offset the loss of muscle during moderate calorie restriction.
- Exercise above usual training levels must be chosen carefully to prevent overuse injuries.
Unfortunately, many athletes fall prey to the quick fixes and rapid weight loss programs that are so heavily advertised. These programs generally suggest severe calorie restriction so weight loss is rapid. However, it is recommended that athletes consume no less than 30 kcal per kilogram of body weight daily. For example, a 154-pound (70 kg) athlete who wants to lose body fat should not typically consume less than 2,100 kcal daily. This caloric level is above resting metabolic rate and is not considered a starvation-type diet. Caloric restriction below this level will typically not provide enough of the carbohydrate, protein, and fat needed to maintain training or conditioning.
A tool that can help athletes create a personalized fat loss plan is the daily energy intake and expenditure estimates described earlier in this chapter. A good rule of thumb is to create a daily calorie deficit of about 500 kcal. For example, an athlete may look at his usual food intake and activity level and find that he could realistically decrease his food intake by 400 kcal daily and increase his exercise by 100 kcal daily. In some cases, such as with small-bodied athletes, a 500 kcal daily deficit would be too much, but a 200 kcal decrease in intake and a 100 kcal increase in exercise (such as resistance exercise) would be achievable, although fat loss would occur at a slower rate.
Once the athlete has established a daily total caloric intake goal, she must determine the distribution of calories for a weight loss diet. Approximately 1.5 grams of protein per kilogram of body weight, or 20 percent of the total calories, should come from protein to help preserve muscle mass and metabolic rate. For example, the 154-pound (70 kg) athlete would need about 105 grams of protein daily, an amount that is not difficult to obtain from food. The majority of the remaining calories should come from carbohydrate, but it is important that the diet have sufficient fat (~20 to 25 percent of total calories) to satisfy hunger. Generally, alcohol is eliminated from the diet when an athlete is trying to lose body fat.
Athletes may find it beneficial to eat six small meals or snacks daily. If possible, each meal or snack should contain some carbohydrate, protein, and fat to keep blood sugar level stable, to repair and protect muscle, and to keep the athlete from getting too hungry.
To summarize, it is typically recommended that athletes who want to lose body fat do the following:
- Consume no less than 30 kcal per kilogram of body weight daily
- Create a calorie deficit of about 300-500 kcal daily, with some of the deficit resulting from a reduction in food intake and some resulting from an increase in physical activity (adjust as necessary)
- Consume about 1.5 grams of protein per kilogram of body weight daily
- Eat six small meals or snacks daily
- Continue or include resistance training to help preserve muscle mass
Learn more about Fundamentals of Sport and Exercise Nutrition.