The sport (or culture) of bodybuilding is older than much of the nutritional and metabolic science we take for granted today. For decades, traditions have been passed along during small talk between sets and, perhaps even more significantly, through bodybuilding magazines. In this day and age, however, with scientific information just a click away, I thought it would be good to address some of the critical aspects of preparing for a bodybuilding contest—namely diet and supplementation, from a research-based perspective. 

A recent paper published in the Journal of the International Society of Sports Nutrition did an excellent job of addressing the important questions that come up when preparing a pre-contest diet. One of the biggest questions, and the first that must be addressed, is how many calories should be consumed. Obviously, this is going to depend on your body size and body composition, but regardless of your size, the same principles apply. The first principle is that the greater the caloric deficit you impose, the more muscle you will lose. Aggressive dieting that results in sudden and dramatic weight loss can lead to equal amounts of muscle and fat being lost at the same time. Keep in mind that the body can break down muscle tissue five times faster than it can build it, so you want to do everything you can to protect all your hard-earned muscle as you prepare for your contest. Research on the subject indicates that a rate of weight loss equaling no more than 0.5–1% of bodyweight per week is going to reduce the loss of muscle mass. For most bodybuilders, this means no more than one to two pounds per week.

The second principle is that the leaner you are, the greater the percentage of muscle you will lose as you drop weight. There is a limit to the amount of energy your body fat can supply. For example, it has been estimated that each pound of body fat can supply no more than 31 kcals per day. That’s a maximum of 31 calories, with the assumption that conditions are perfect for fat mobilization. In the real world, things are seldom perfect, so the reality is it will be a little less than 31 calories in most cases. Let’s look at an example: If you have 100 pounds of body fat, like the folks who compete on those weight-loss competitions on TV, your own fat can provide 3,100 kcals per day. That means you can create a 3,100-calorie daily deficit without really forcing your body to tap into your muscle mass for extra calories. If, on the other hand, you only have 20 pounds of body fat (e.g., a 200-pound bodybuilder at 10–11% body fat), your own fat can at best only provide 620 calories per day. So if you create a caloric deficit larger than 620 calories, be it through diet, exercise, or both, your body must use protein for fuel—it has no other option. I know some of you are saying, yeah, but that’s all fat calories—doesn’t your body also need some sugar for fuel? Yes, it does, and we’ll get into that in a moment, but for now, understand that the leaner you get, the more difficult it is to keep from losing muscle as you diet because there is a limit to the rate that your body can release fat for fuel. 

The third principle is that the longer you keep the body in a caloric deficit, the more it will adapt by slowing the metabolic rate (i.e., calories required per pound of body weight). In those studies that have been done, the metabolic rate has been shown to fall as little as 80 calories per day to as much as 500 calories per day! This tells us that adjustments will need to be made along the way to account not only for a reduction in caloric requirements due to body-weight loss, but also because your metabolic rate will slow, making weight loss slow down with it.

Of course, not only calories matter during a diet—the source of those calories is very important. Protein intake is critical if your goal is to retain as much muscle as possible during your diet. The usual recommendation of a gram per pound of body weight may not be enough to minimize muscle loss. Eating a gram per pound of body weight can still lead to as much as one half to one pound of muscle loss every two weeks depending on the size of the caloric deficit and the level of body fat you have at the time. A recent review of results from studies involving lean weight lifters shows that 1.5 grams of protein per pound of body weight will likely be required to reduce muscle loss the closer you get to the day of the show. 

Everybody is in agreement when it comes to protein recommendations, but when it comes to carbohydrates, opinions vary quite a bit. Some say you can’t get really lean without going ketogenic, while others say that simply reducing calories is a better strategy. Regardless of current fads, if your goal is to keep as much muscle mass as possible, keep your carbs as high as you can while still being able to lose body fat. I know a lot of guys and gals who jump right into a low-carb diet and add cardio all at the same time. This is the worst thing you can do if you’re trying to keep your muscle. Add the cardio first while keeping carbs where they are. Then, in a stepwise fashion, begin to drop your carbs. Carbohydrates regulate substrate utilization. 

In other words, carbohydrates are preferentially used as fuel when both carbs and fat are present. The utilization of fat for fuel will be in proportion to the carb deficit. There is a threshold, however, below which lowering carbs further does nothing to hasten fat loss while greatly increasing muscle loss. So getting fanatical about avoiding carbs is not only unnecessary but quickly becomes detrimental, especially for a drug-free bodybuilder. Research indicates that if one is able to keep carbs at around 50% of total calories, along with adequate protein intake, muscle loss can be adequately minimized. 

Last but not least, fat. Current fat-intake recommendations stem from maximizing testosterone levels. Compared with insulin and IGF-1, however, testosterone is not as potent at preserving muscle mass for the natural bodybuilder. Insulin and IGF-1 are related to total carbohydrate intake. Again, if the goal is to preserve muscle mass, reduce fat first if it means carbs or protein would be reduced below ideal ranges. A fat intake of 15–20% of total calories would be appropriate.

To summarize, total calories should not be cut below the amount that results in one to two pounds of weight loss per week. As you get closer to the contest date, you will want to reduce weight loss to one pound per week to save more muscle. That should help you plan how many weeks you need to diet. Protein should range from one to 1.5 grams per pound of body weight. Carbohydrates should stay as high as possible, while protein should be kept in the ideal range and still allow for one to two pounds of weight loss per week. Fat can make up the rest and should fall between 15-20% total calories. All of this will give you a starting point. Careful adherence to your diet will make adjustments more effective as necessary. 

And last but not least, give yourself plenty of time to get into contest shape. It’s better to be contest ready at least two weeks before the show, then give yourself time to increase your calories slightly and fill out a little bit. You will be fuller and have better control over water retention.