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Muscle-Building and Fat-Burning Answers From Two Top Researchers

From Featured Story: The Science of Bodybuilding

Part 1

You probably know of Gabriel J. Wilson, M.S., CSCS, and his brother Jacob M. Wilson, Ph.D, CSCS. They are renowned scientists in their field and have written numerous science features for IRON MAN. They also have a popular Web site,, that presents the latest scientific findings pertaining to the world of muscle and rippedness.

These gentlemen know what they’re talking about and have spearheaded many research studies throughout their academic careers. In other words, the Wilson brothers have answers that can help you—and me—get a bigger and better physique. In fact, these men are so thorough, they insisted on providing references to verify their answers.

IM: What’s your opinion of doing cardio on an empty stomach first thing in the morning? Won’t that cause catabolism?

WB: The basic rationale behind fasted cardio is that the rate of fat oxidation is generally in proportion to the amount of free fatty acids in the bloodstream, and free fatty acids are higher in a postabsorpative—i.e., fasted—state, when insulin levels are low. While that is true, there are several potential side effects from fasted cardio.

As you indicated in your question, after an overnight fast you are in a catabolic state, with protein degradation exceeding rates of protein synthesis. Adding cardiovascular exercise on top of that will further induce muscle catabolism.1

An additional problem is that you must delay the breakfast meal. In fact, some prescribe delaying eating for several hours after the fasted cardio bout to maintain optimal fat oxidation postexercise.2 The first meal may not be eaten until noon. The reason we mention that is, research has shown that skipping breakfast is closely associated with overeating, weight gain and obesity.3 Therefore, skipping breakfast will have a detrimental effect on metabolism for the remainder of the day, resulting in increased hunger and food consumption. All of that is why we don’t recommend doing cardio first thing in the morning on an empty stomach.

So the question is, How do you optimize fat oxidation during cardio without eliminating the breakfast meal? The answer is to perform low-to-moderate-intensity cardio after a HIIT session.

High-intensity exercise has been shown to rapidly increase the amount of free fatty acids in the bloodstream, lower blood insulin levels and increase fat oxidation after the bout.4 Accordingly, studies have shown that performing low-to-moderate-intensity cardio after high-intensity exercise—sprints or weight training—increases fat oxidation.5,6 That method allows you to mimic the effect of doing cardio in a fasted state without the harmful effects of skipping breakfast.

IM: I’ve seen research showing that more than 50 percent of excess protein turns to glucose. If that’s the case, and bodybuilders are eating a lot of protein every few hours, how can they ever burn bodyfat?

WB: That’s true—and we contend that most bodybuilders are overconsuming protein. But optimal protein intake and frequency are beyond the scope of this answer. In short, we recommend that bodybuilders focus on the leucine content of their proteins. As long as you surpass a leucine threshold of 2.5 grams per feeding—up to four grams for really big guys—you’re going to optimize muscle protein synthesis.

Therefore, you can lower your protein intake by getting higher-quality proteins—whey has 11 percent leucine, eggs have 9 percent leucine, and meats have around 8 percent vs. plant proteins, which are usually around 6 percent. You can also supplement with branched-chain amino acids.

Getting back to the question, how can bodyfat be lost even with excessive protein intakes? Two reasons: First, fat loss is ultimately going to be the product of creating a calorie deficit. So, even if you’re getting an excessive amount of protein, as long as you create a deficit, you will lose fat. Second, hepatic glucose—made in the liver via gluconeogenesis using protein—stimulates much less insulin production and, consequently, is less prone to stimulate fat increases than glucose that comes directly from the diet.

In fact, the gluconeogenic response caused by higher protein intakes is actually a positive adaptation that can lead to greater fat loss and satiety—particularly when combined with lower carbohydrate intakes. Dr. Layman and his lab at the University of Illinois have shown that to be the case in a number of studies.7

To summarize, what happens when you follow higher-protein, lower-carbohydrate diets—40 percent carb, 30 percent protein—is that you make a metabolic shift from being carb dependent to being carb independent. That’s accomplished by decreasing insulin levels (a hypoglycemic hormone) and increasing glucogon levels (a hyperglycemic hormone). Glucogon is able to activate enzymes that turn protein to glucose, as well as activate lipolytic enzymes, meaning those that break down fat.

Certain amino acids, such as leucine, are also able to stimulate gluconeogensis directly. Now your body has the ability to produce its own glucose and sustain a steady flow of blood glucose and low-to-moderate insulin levels. Conversely, Dr. Layman’s research has shown that those who follow lower-protein, higher-carbohydrate diets—55 percent carb, 15 percent protein—have constant spikes and fluctuations in blood glucose and insulin because they are carb dependent. That results in greater hunger and less fat loss.

Overall, the message we’re trying to get across is that bodybuilders definitely need to work on improving their efficiency of protein intake—but maintaining relatively high levels of protein is still important to maximize fat loss and muscle mass.

IM: Okay, so for the average 200-pound bodybuilder, what are the best macronutrient percentages for building mass and losing fat?

WB: We generally don’t prescribe macronutrient percentages for gaining mass—especially for athletes who have extreme ranges of caloric needs. For instance, say we were to recommend getting 40 percent protein for bulking. If an ectomorph who has a ridiculous metabolism that requires 7,000 calories daily to gain weight were to apply that advice, he would end up eating 700 grams of protein! That’s entirely unnecessary.

First, if you want to gain weight, you will have to be in a caloric surplus; and if you want to lose weight, you will have to be in a deficit.

On a bulk you want your protein to be moderate, and make sure you’re getting ample leucine. Getting 400 grams of protein a day is not the answer to getting huge. You can easily get away with a gram of protein per pound of bodyweight if it’s coming from efficient protein sources with high leucine contents. Instead, you should focus on increasing your fats and carbohydrates.

We recommend a minimum of 60 to 80 grams of fat daily, as that appears to maximize testosterone.8 The amount of carbohydrates is going to depend on your genetics and goals. For ectomorphs and mesomorphs we would recommend fulfilling the remainder of your caloric needs by increasing your carbohydrates—though don’t be shy about adding a little more fats, as long as they are healthful fats like monos and polys. But for endomorphs, who tend to be more insulin resistant, we suggest being more cautious with carbohydrate intake. We recommend that this population slowly increase their carbohydrates until they find a comfortable level of steady weight gain and high energy, without excessive fat gain.

IM: But to lose fat, they should reduce carbohydrates, correct?

WB: Yes, decreased carbohydrates have been shown in countless studies to be critical for weight loss.9 So the primary focus will need to be on shaving your carbohydrates down steadily until you hit your desired goals. It appears that a 1-to-1 ratio of carbs to protein per meal can optimize fat loss9—though some endomorphs may have to decrease their carbohydrates even more, in particular for contest preparation.

IM: What’s the ideal preworkout meal, and how many hours should it be eaten before training?

WB: A light meal one to two hours prior to your workout is ideal. It should have ample amounts of carbohydrates—up to 50 to 70 grams—enough protein to stimulate protein synthesis—30 grams or just branched-chain amino acids—and be low in fats. Lower-glycemic carbs appear to be ideal preworkout, as they have been shown to help sustain energy and performance, as well as delay fatigue.10 A sample meal would be one cup of oatmeal and 30 grams of whey protein—or just BCAAs.

IM: You mentioned low-glycemic carbs. Is fruit bad for dieting bodybuilders?

WB: Fruits have often gotten a bad rap in the bodybuilding community because of their high fructose contents. Fructose should not be abundant in your diet, as it preferentially restores liver glycogen—when we want muscle glycogen to be full—and gives a poor insulin/leptin response. Also, when in excess, fructose can increase triglyceride synthesis and promote insulin resistance.11 But most of the studies that show that are using extreme amounts of fructose—like 60 percent of the diet.

In contrast, low amounts of fructose—say, five to 10 grams—eaten 30 to 60 minutes before, but not directly with, a starchy-carbohydrate meal, have actually been shown to increase insulin sensitivity and improve blood glucose profiles.12

It’s also important to note that fruits have many inherent properties that are beneficial to bodybuilders. Their tremendous nutrient profiles—which include antioxidants, polyphenols, fiber, vitamins and minerals—can improve health, insulin sensitivity and satiety.

The key here is going to be eating fruits that have high nutrient profiles and low calorie densities—less than five to 10 grams of fructose per serving. We recommend strawberries, oranges, apples and other fruits that have low-glycemic indexes because they contain fewer calories but are rich in fiber and nutrients. Including them in your diet is a great way to increase the palatability of your foods and will help you stick with your plan.

In Part 2 of this interview the Wilsons discuss cheat days during a diet, the anabolic properties of insulin and how to maximize them, whey and casein proteins, minimizing cortisol and maximizing fat loss.

Editor’s note: Gabriel Wilson is a Ph.D. candidate in nutrition in the Division of Nutritional Sciences, University of Illinois, Urbana-Champaign. He is researching optimal protein requirements for muscle growth. Gabriel is also vice president of Jacob Wilson, Ph.D., is a professor of exercise science and researcher in the Department of Exercise and Sports Sciences at the University of Tampa. Jacob is also president of


1 Fujii, N., et al. (2000). Exercise induces isoform-specific increase in 5’AMP-activated protein kinase activity in human skeletal muscle. Biochem Biophys Res Commun. 273:1150-1155.

2 Bahadori, B., et al. (2009). A "mini-fast with exercise" protocol for fat loss. Med Hypotheses. 73:619-622.

3 Leidy, H.J., and Racki, E.M. (2008). The addition of a protein-rich breakfast and its effects on acute appetite control and food intake in ‘breakfast-skipping’ adolescents. Int J Obes (Lond) 34:1125-1133.

4 Kindermann, W., et al. (1982). Catecholamines, growth hormone, cortisol, insulin and sex hormones in anaerobic and aerobic exercise. Eur J Appl Physiol Occup Physiol. 49:389-399.

5 Goto, K., et al. (2007). Effects of resistance exercise on lipolysis during subsequent submaximal exercise. Med Sci Sports Exerc. 39:308-315.

6 James, D.V., and Doust, J.H. (1998). Oxygen uptake during moderate-intensity running: response following a single bout of interval training. Eur J Appl Physiol Occup Physiol 77:551-555.

7 Layman, D.K. (2003). The role of leucine in weight-loss diets and glucose homeostasis. J Nutr. 133:261S-267S.

8 Volek, J.S., et al. (1997). Testosterone and cortisol in relationship to dietary nutrients and resistance exercise. J Appl Physiol. 82:49-54.

9 Layman, D.K., et al. (2003). A reduced ratio of dietary carbohydrate to protein improves body composition and blood lipid profiles during weight loss in adult women. J Nutr. 133:411-417.

10 DeMarco, H.M., et al. (1999). Pre-exercise carbohydrate meals: application of glycemic index. Med Sci Sports Exerc. 31:164-170.

11 Samuel, V.T. (2009). Fructose induced lipogenesis: from sugar to fat to insulin resistance. Trends Endocrinol Metab.

12 Heacock, P.M., et al. (2002). Fructose prefeeding reduces the glycemic response to a high-glycemic-index, starchy food in humans. J Nutr. 132:2601-2604. IM

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