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As a bodybuilder, you've heard this many times: boosting your body's production of testosterone and growth hormone is absolutely essential to fuel muscle growth. You're probably unaware, though, that there may be an even more vital component, one that could clearly make the difference between failure and success in building a bigger, stronger physique. It's called insulinlike growth factor-I, or IGF-I, a naturally occurring protein very similar in structure to insulin, another important anabolic hormone. If you've been reading FLEX for any length of time, you're probably at least somewhat familiar with the term. However, you probably don't know the complete story of IGF-I; after all, even scientists and bodybuilding experts get it wrong. That's because IGF-I is a somewhat new discovery — and as with any new discovery, researchers learn more about it with each passing day.
The key component of the FLEX Growth-Factor Diet is raising IGF-I levels by eating the right food at the right time, and combining a high-protein, low-carbohydrate diet with the right supplements to help boost your muscle and strength gains to new heights. Altogether, it's a comprehensive nutrition and supplement plan that leaves nothing out — use it for the next six to eight weeks and you'll be growing like never before.
IGF-I hits the bloodstream when growth hormone travels to the liver and influences the release of IGF-I from that organ. In the bloodstream, IGF-I can travel to tissues, such as muscle, to influence growth. This means that IGF-I levels in blood often mirror GH levels; in fact, blood IGF-I concentrations are often used to estimate GH quantities.
For years it was believed that only the liver produced IGF-I. Recently, it was discovered that IGF-I is also manufactured by muscle fibers, mostly the fast-twitch variety. During weightlifting, muscles produce more IGF-I in response to the mechanical stress placed on them by the resistance of the weights. This IGF-I is the most critical ingredient for muscle growth. IGF-I encourages muscle growth in three major ways.
In this article, we provide a sample one-day growth-factor meal plan, designed for an average 180-pound bodybuilder who is striving to pack on lean mass. To make those gains, be sure to consume enough total calories, as higher-calorie diets are associated with higher IGF-I levels. Thus, this diet provides approximately 19 calories per pound of bodyweight per day, or just over 3,400 calories for a 180- pound bodybuilder. (Adjust this figure — and your intake of each macronutrient described in the following paragraphs — based on your own weight.)
Approximately 40% of your total daily calories should come from protein, or about two grams of protein per pound of bodyweight. The best protein sources for boosting IGF-I are dairy, fish (choose higherfat fish like salmon, white albacore tuna and catfish), beef, poultry and eggs. Dairy protein is great not only because it supplies both whey and casein protein, but also, research has shown, because it boosts IGF-I levels, possibly due to the small amount of IGF-I found in milk.
Thirty percent of your total calories, or about 1.5 g per pound of bodyweight, will be coming from carbs. Higher carb intake is associated with low IGF-I levels; you can still eat carbs at most meals throughout the day, but generally avoid them in the evening. Choose slow-digesting carbs, such as oatmeal or fruit at breakfast, whole-wheat bread at lunch and fruit before workouts. Eat fruits high in lycopene, such as pink grapefruit, watermelon and dried apricots — lycopene has beneficial effects on IGF-I.
You will also be getting carbs from milk and other dairy products. Those who have trouble digesting milk sugar (lactose) or those who are not used to drinking much milk may consider using the enzyme supplement Lactaid (taken with dairy products or in milk containing the supplement).
After workouts, consume fastburning carbs, such as rice cakes, white bread, plain bagels or white potatoes. These will bump up your insulin levels to help drive muscle growth and push carbs into your muscles, where they'll be stored for fuel to be used in your next workout. Carbs also pull water into muscles; that will help keep your muscles looking full. Finally, insulin is important for drawing creatine into muscle cells; the creatine may help to boost muscle levels of IGF-I. During this diet, maintain a moderate fat intake — about 30% of total daily calories. This is somewhat high by bodybuilding standards, but the healthy fats consumed won't necessarily result in added bodyfat; in fact, they'll actually help you drop it while you simultaneously gain muscle mass. Choose from avocados, mixed nuts, olive oil (as in salad dressing), olives and peanut butter, as well as egg yolks (from whole eggs) and fatty fish (such as salmon). Eating some fat is important for keeping IGF-I and testosterone levels up.
Armed with the accompanying diet, the supplement program and a bodybuilding-training regimen that uses the tips provided in the Training Factors sidebar, you will be able to drive growth effectively and put IGF-I to work for you. It's a potent blueprint that — although basic at its core — can revolutionize your personal gain plan, especially if your diet has been off-track until now. Even if you have been eating a bodybuilder-friendly diet, this could be the next step up that you need for real, tangible, perhaps even extraordinary, results. Are you in? FLEX