A triathlete recently wrote to ask how he could lose weight before an important race he has coming up in a few weeks. He'd like to shed 5 pounds (2.3kg) before his A-priority race. There is indeed a cost to be paid when carrying excess fat around. One extra pound (0.45kg) costs about 2 seconds per mile running and takes roughly 3 watts to get it up a hill on a bike. So that 5 pounds represents about 10 seconds per mile running and 15 watts on a climb. That's significant and so dropping a bit of excess baggage has the potential to make him faster on race day. The problem is timing. Trying to lose weight while also training at a high level is not conducive to high performance. Losing weight is additional stress for a body already dealing with the stress of quality training. Recovery will be compromised. Such a path is likely to lead to illness, injury and possibly overtraining.
Nevertheless, I told him I'd post an article I wrote on this sometime back. Here's a quick review of the literature on weight loss from an athletic perspective...
What’s the best way go about it? Should you reduce your intake of fat, or perhaps carbohydrate, which seems to be the trend recently. Or should you simply eat fewer calories? Or maybe you should train more. What’s the best alternative?
There have been many studies conducted to answer the question regarding the relative mix of macronutrients in the diet in order to lose weight. The majority of the results report the same conclusion: To reduce body weight, it doesn’t matter whether you eat a high-carbohydrate or a high-fat diet as long as total calories are reduced. For example, in one study, three groups of women dined on a 1,200-calorie-per-day diet for 10 weeks . One group ate 25 percent carbohydrate, another ate 45 percent carbohydrate, and the third ate 75 percent carbohydrate. Each of the diets contributed to weight loss with no significant differences between the groups.
In similar research, 43 women spent six weeks in a hospital on a 1,000-calorie-per-day diet with about half of them eating 53 percent fat and 15 percent carbohydrate . The other half ate 26 percent fat and 45 percent carbohydrate. Again, there was no significant difference in weight loss between the two groups, although the high-fat group lost slightly more weight – about three pounds (1.4kg).
From our perspective, the problem with most all of the studies of weight loss is that they use obese, sedentary subjects making the conclusions questionable for athletes. But a study on the effect of diet on coronary heart disease risk factors of runners may provide some better insights. The subjects were serious runners who ate either a 16-percent- or a 42-percent-fat diet for four weeks each . At the end of the test periods, there was no significant difference between the two diets in terms of the subjects’ weights or body compositions. (It’s interesting to note that risk factors for heart disease improved on the higher-fat diet.) So the lessons of the previously mentioned studies appears to hold true for athletes as well – it doesn’t matter what the carbohydrate-fat mix of your diet is so long as you reduce calories.
Unfortunately, there have been few studies of serious athletes that strictly examined weight loss. But in 1985, McMurray and colleagues examined the issue in exactly the way athletes view the challenge . The scientists attempted to find out if reducing caloric intake or increasing training workload was more effective in dropping excess body fat. They had six, endurance-trained males create a 1,000-calorie-per-day deficit for seven days by either exercising more while maintaining their caloric intake, or by eating less while keeping exercise the same. With 1,000 calories of increased exercise daily (comparable to running an additional 10 miles or cycling about 30 more miles each day), the subjects averaged a 1.67-pound (0.76kg) weight loss in a week. The subjects eating 1,000 fewer calories each day lost 4.75 (2.16kg) pounds on average for the week. According to this study, the old adage that “a calorie is a calorie” doesn’t hold true. At least in the short term, restricting food intake appears to have a greater return on the scales than does increasing training workload.
Notice that I said “on the scales.” The reduced-food-intake group in this study unfortunately lost a greater percentage of muscle than did the increased-exercise group. That is an ineffective way to lose weight. If the scales show you’re lighter, but you have less muscle to create power, the trade off is not a good one.
How can you reduce calories and yet maintain muscle mass? Unfortunately, that question hasn’t been answered for athletes, but it has been for sedentary women. I suspect the conclusions are still applicable. A few years ago Italian researchers had 25 subjects eat only 800 calories a day for 21 days . Ten ate a diet made up of 45-percent protein and 35-percent carbohydrate. Fifteen ate 20-percent protein and 60-percent carbohydrate. Both were restricted to 20 percent of calories from fat. The two groups lost similar amounts of weight, but there was a significantly greater loss of muscle on the high-carbohydrate, low-protein diet.
So what’s the bottom line? It appears that when calories are reduced to lose weight, which is more effective than increasing training workload, the protein content of the diet must be kept at near normal levels. This, of course, assumes that you’re eating adequate protein before starting the diet, which many athletes aren’t. When training hard, a quality source of protein should be included in every meal. This may be some combination of meat, fish, shellfish, poultry and eggs.
1. Alford, B.B., et al. 1990. The Effects of Variations in Carbohydrate, Protein, and Fat Content of the Diet Upon Weight Loss, Blood Values, and Nutrient Intake of Adult Obese Women. J Am Diet Assoc 90(4):534-540.
2. Golay, A., et al. 1996. Similar Weight Loss with Low- or High-Carbohydrate Diets. Am J Nutr 63(2):174-178.
3. Leddy, J., et al. 1997. Effect of a High or Low Fat Diet on Cardiovascular Risk Factors in Male and Female Runners. Med Sci Sports Exerc 29(1):17-25.
4. McMurray, R.G., et al. 1985. Responses of Endurance-Trained Subjects to Caloric Deficits Induced by Diet or Exercise. Med Sci Sports Exerc 17(5):574-579.
5. Piatti, P.M., et al. 1994. Hypocaloric, High-Protein Diet Improves Glucose Oxidation and Spares Lean Body Mass: Comparison to Hypocaloric High Carbohydrate Diet. Metab 43(12):1481-1487.