Intake For Performance Enhancement

Much of the discussion on energy intake focuses on the optimal distribution of the energy substrates: carbohydrate, protein, and fat. Despite the popular recommendations for high-protein, low-carbohydrate diets, there is no question that focusing on a diet high in complex carbohydrates, moderate in protein, and relatively low in fat is performance enhancing. But this discussion has little meaning in the face of energy intake inadequacy. Put simply, it doesn't matter if high-octane fuel is put in the system if there isn't enough fuel to get you where you want to go.

Weight and lean-mass stability are the best indicators that energy intake matches need. A failure to consume sufficient energy leads to either a reduction in weight or a reduction in lean mass (or both) as the body tries to compensate for this deficiency. For most athletes, a lower relative lean mass and higher relative fat mass is not desirable and is a physiological marker associated with decreased performance. In what must be considered a terribly unwise reaction to this relatively higher fat mass, athletes commonly reduce energy intake still further to reduce the excess fat. The impact of this constant ratcheting down of energy intake is weight loss with a greater loss of lean mass than fat mass, with fat constituting an ever-higher proportion of body weight.^7,8 If caloric intake is inadequate, the body reduces the metabolic mass (i.e., the muscle mass) to make a downward adjustment in the metabolic rate and the need for calories.

It is possible that this cycle of lowering energy intake to adapt to a constantly rising relative fat mass is predictive of the eating disorders seen too often in athletes where appearance plays a factor in a sport's subjective scoring.⁹ To emphasize this point, it should be noted that anorexia nervosa victims at death show a terrible loss of weight and a terrible loss of lean mass (the weight of the heart is typically 50 percent of normal) but have a relatively high body fat percentage. Severely deficient caloric intakes, therefore, lead to a greater wasting away of lean mass than of fat mass.¹⁰ The concept that a significant reduction in calories (i.e., dieting) results in an improved body profile and body composition simply does not stand up to scrutiny. Although a short-term lowering of body weight may be temporarily associated with enhanced performance, the long-term effect of such low-calorie diets is to lower the intake of needed nutrients (a problem that can manifest itself in disease frequency and increased risk for low bone density); to lower the muscle mass (as an adjustment to the inadequate caloric intake); and to regain the weight, which is made up of less lean tissue and more fat. To make matters worse, the lowering of lean mass makes eating normally without weight gain more difficult.

A microeconomic view of the energy balance issue may shed some light on how athletes should eat to achieve an optimal body composition that enhances performance. A study of four groups of national-level female athletes (rhythmic gymnasts, artistic gymnasts, middle-distance runners, and long-distance runners) found that those who deviated most widely from perfect energy balance during the day had the highest body fat levels, regardless of whether the energy deviations represented surpluses or deficits.¹¹ In fact, the rhythmic gymnasts, who as a group had the most pronounced energy deficits (nearly-800 kcal), had the highest body fat percent of all the groups assessed, while middle-distance runners had the best within-day energy balance and the lowest body fat percents.

This strongly suggests that the common eating pattern of athletes, which is typified by infrequent meals with a heavy emphasis on a large end-of-day meal, is not useful for meeting athlet c goals because it is guaranteed to create large energy deficits during the day. Although this energy deficit may be made up for at the end of the day to put an athlete in an energy-balanced state, this eating pattern is typified by weight stability but higher than desirable body fat levels.

The reason for the higher body fat level becomes clear when you consider how blood sugar fluxes (after a meal, it rises, levels off, and drops over a period of 3 hours). With delayed eating, blood sugar drops and the amino acid alanine is recruited from muscle tissue to be converted to glucose by the liver. Although this stabilizes blood sugar, it does so at the cost of the muscle mass. In addition, both low blood sugar and large meals are associated with hyperinsulinemia, which encourages the manufacture of fat. So, delayed eating followed by an excessively large meal, which is typical of the athletic eating paradigm, is an ideal way to lower muscle mass and increase fat mass . . . not what athletes want to do. Frequent eating reduces the size of within-day energy deficits and surpluses and helps stabilize blood sugar.

Many studies assessing eating frequency have come to the same conclusion: The more frequent the eating pattern, the lower the body fat and the higher the muscle mass.^12-14 In addition, frequent eating patterns provide a simple, workable strategy for increasing energy intake while simultaneously reducing GI discomfort associated with larger meals.¹²

A study assessing the impact of meal frequency on body composition and weight in boxers found that, even with isocaloric intakes (both groups had the same caloric intake for 2 weeks), the group consuming two meals each day experienced a significant reduction in lean body mass, whereas the group consuming six meals each day did not.⁶ In another study of wrestlers, athletes who recorded cyclic weight changes, typified by long periods of very low caloric intakes, had lower metabolic rates, suggestive of a loss of lean body mass.¹⁵

These studies suggest that large within-day energy deficits clearly cause muscle catabolism, which can be avoided by supplying energy in smaller but more frequent meals. This finding is consistent with a recent study of 60 male and female collegiate athletes that assessed the impact of adding a 250-calorie snack or a noncaloric placebo between each major meal and after dinner (i.e., between breakfast and lunch, between lunch and dinner, and after dinner, for 750 calories provided as snacks each day). After 2 weeks of this protocol, the group consuming the caloric snack experienced a significant reduction in body fat, a significant rise in lean body mass, a significant improvement in anaerobic power and anaerobic endurance, no change in weight, and no change in total caloric intake.¹⁶ Weight stayed the same because energy intake did not change (an important principle of energy thermodynamics), a result that presents an interesting point. When snacks were provided with no instructions regarding the other meals, the athletes spontaneously reduced the size of the other meals to compensate for the snacks. A failure to do so would have increased total caloric intake and resulted in a weight gain.

The snacks were removed 2 weeks into the stud . The athletes were remeasured 4 weeks later; they had assumed their old eating patterns and returned to baseline values for body fat and muscle mass. The findings of this study make it clear that an athlete's eating pattern will default to his or her usual practice (e.g., two or three meals a day, with the largest meal at the end of the day) unless a new pattern becomes the accepted standard. Indeed, studies have found that the environment (e.g., who the athletes tend to eat with; food availability) plays a major role in eating patterns.¹⁷ Getting athletes to eat more frequently on their own, in opposition to the environmental norm, is extremely difficult.

Animal studies have also found benefits to increasing meal frequency so that large within-day energy deficits and surpluses can be avoided. A study using dogs found that providing a set amount of calories in small but frequent meals rather than large infrequent meals significantly reduces the insulin response to food, even in dogs fed a high-carbohydrate meal. In addition to this clear benefit, more meals result in higher thermogenesis (faster energy metabolic rate) and better fat utilization.¹⁸ What does this mean for athletes? A high insulin response to food translates into high fat production, so having a reduced insulin response means less fat production. Having a faster metabolic rate makes it easier for athletes to eat without getting fat because more calories are being burned per unit of time. These factors, plus a more efficient fat utilization, all translate into eating more, taking in more nutrients, maintaining muscle mass, and lowering body fat percentage. A failure to eat frequently, causing a mini-starvation state during the day, has just the opposite effect on metabolic rate. The resulting lower metabolic rate is associated with a higher fat mass and more difficulty eating normally without gaining fat.^{19- 21}The act of eating more frequently, in and of itself, appears to play a role in the thermic effect of food (the number of calories burned as a result of eating; a higher burn rate is considered good because it is associated with lower body fat). The thermic effect of food is higher in subjects eating at regular, short intervals when compared with subjects eating at irregular, longer intervals.²²

The benefits of eating frequently enough to reduce the magnitude of within-day energy deficits and surpluses go beyond body composition, weight, and performance. There is also evidence that people with frequent eating patterns have lower serum lipid levels, a risk factor in cardiovascular disease.²³ A study assessing the impact of food restriction during the period of the Ramadan fast found that insulin production was increased, as was the production of leptin (a hormone produced by fat cells), both of which are associated with a greater fat-mass production.²⁴

Many athletes concerned about weight have learned to cope with the feeling of low blood sugar by consuming a diet product (diet colas are popular). Although these diet products do nothing to resolve the very real physiological need for energy to maintain an adequate blood sugar, they do provide a central nervous system stimulant (usually caffeine) that masks the sensation of hunger. However, since this strategy maintains the low blood sugar level, the outcome will inevitably be less muscle and more fat. It is clear from these studies that the only appropriate strategy for weight loss is a subtle energy deficit that results in only a slight deviation from a within-day energy-balanced state.

What are athletes to do? Never get hungry. This is not easy with a typical threemeal-a-day eating pattern, which provides for a refueling stop every 5 to 6 hours, and the typical athlete eating patterns that heavily backload intake make it even more difficult. Since blood sugar is known to rise and fall in 3-hour units, it makes sense to ave planned snacks. If an athlete is weight stable, the best way to initiate this process is to eat a bit less at breakfast, eat the remainder at midmorning, and do the same for lunch and dinner. Total caloric intake will remain the same, but the athlete will avoid sharp energy deficits and surpluses during the day. Besides the improved nutrient intake and better body composition associated with this type of eating pattern, athletes can also expect improved mental acuity and enhanced athletic performance.

Considerations For Fluid Intake

Considerations For Energy Intake