For years, bodybuilders have been told to eat low-carb/ high-protein diets to control insulin. The traditional way of thinking has been: carbs = insulin = fat bodybuilder. The newest research shows that protein is also a source of insulin production. In fact, some proteins can be just as potent of a stimulus for insulin as carbs. Researchers fed participants two meals containing the same calories (i.e., 675 calories), but one meal contained 21 grams of protein and 125 grams of carbs. The other meal contained 75 grams of protein and 75 grams of carbs. According to the bodybuilding dogma that carbs increase insulin, the meal with the higher carbs should have spiked insulin higher, but it didn’t.

The researchers found that the blood glucose response was much higher in the meal with more carbohydrates, however the insulin response wasn’t higher despite having higher carbs. So proteins can have just as profound of an impact on insulin as carbs. In another study, researchers examined the insulin response of four proteins. The subjects were fed fish, whey protein, turkey, and egg. The insulin responses were lower in the egg, followed by turkey, then fish, with whey having the highest insulin response. So food sources of high protein with the highest leucine content resulted in the highest insulin responses.

What most bodybuilders don’t realize is that insulin suppresses appetite. When the researchers measured hunger responses of the previous study, whey protein had the highest impact with reducing hunger, which was associated with higher insulin responses. Protein and carbs cause rapid increases in insulin. Bodybuilders should forget the notion that carbs are evil, because proteins as well as carbs increase insulin. Many obese people are insulin resistant, which can cause enhanced weight gain. The following studies should bring awareness to the fact that many proteins can spike insulin similar to that of carbohydrates.

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Protein’s Effect on Appetite: Proteins and How They Work with Your Hormones

Every bodybuilder who’s ever competed in a show knows that a high-protein diet will help suppress appetite, but the physiological mechanisms have been lacking. Researchers took 13 normal-weight and 12 overweight-to-obese men and had them participate in a three-way crossover design, in a random order; each test meal was separated by at least four weeks. The three test meals were: normal protein, containing 14%of calories from protein; medium-high protein, with 25%of calories from protein; and high protein, with 50%of calories from protein. The researchers were looking at several hormones that stimulated appetite and those that inhibited appetite (GLP-1, PYY, and glucagon). When the researchers collected all the data, there was a dose-dependent response of protein intake on GLP-1 (i.e. appetite-suppressant hormone) over the four hours after the meal. The medium-high protein created a 10%higher response than the normal-protein meal, and the high-protein meal produced a 20%higher response. There was a dose-dependent effect on glucagon, with a 47%higher response in the medium-high protein meal compared with the normal protein meal, and a 116%higher response in the high-protein meal. This study demonstrated that protein had a dose-dependent effect on certain satiety-related hormones, namely GLP-1, PYY, and glucagon. Also, the appetite-suppressing hormone CCK was elevated more at four hours in the high-protein condition compared with the other meals. Thus, the impact of protein on these hormones may be one of the reasons why protein helps you feel full. It can also be useful knowledge for off-season training. In order to stimulate the appetite, a bodybuilder may consider cutting back on protein.