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IIFYM Explained


It is the bane of every old-school bodybuilder’s existence. It is the cause of cyber-wars throughout all social media. It has ripped families apart and torn relationships to shreds. It is the Great IIFYM Debate.

While that introduction may have been a little exaggerated, this diet’s impact on the fitness industry can’t be exaggerated. It’s been praised, scorned, lauded, ridiculed (“If It Fits Your Mouth”), and researched, but there’s no denying that it does work. IIFYM, or “If It Fits Your Macros,” is one of the newer kids on the block in terms of contest prep diets. It’s grounded in the theory that the calories from different macronutrients are created equal, and as long as you’re in a caloric deficit, it doesn’t matter what types of proteins, carbs, or fats you eat, you will still lose weight/fat. Conversely, if you’d like to gain weight/muscle, then if you are in a caloric surplus, the same theory applies.

Macronutrient Mystification
This IIFYM versus “traditional diet” controversy isn’t just about the “A calorie is a calorie” paradigm; rather, it’s about people thinking, “A calorie from a Pop-Tart is the same as a calorie from broccoli.” There are a few flaws in this argument right off the bat:

​The Glycemic Index: Even in 2014, the glycemic index (GI) of one’s food is still being used a predictor of various metabolic and health-related conditions.2 Granted, we don’t give as much credence to the GI because it’s very rare that a person will only eat one food as his or her meal, but the GI is still relevant. In a traditional bodybuilding diet, emphasis is placed on “slow-burning,” high-fibre, complex carbs because they keep the body’s insulin levels more stable.3 It’s also been shown that a high-GI meal can increase hunger and stimulate craving centers in the brain compared with a low-GI meal.4,5

The Satiety Index: Satiety refers to how full you are after consuming a food. The satiety index refers to how different foods differ in their satiating capacities. The “gold standard” is white bread, which has an index of 100. With regard to the IIFYM debate, one can see how broccoli and Pop-Tarts are on different ends of the spectrum. Pop-Tarts would obviously be closer to white bread (or 100) on the continuum, and broccoli (as an example of fibrous carbs) would be much lower. When this was tested, protein, fibre, and water contents of the test foods correlated positively with SI scores.1 “Simple carbs” scored lower on satiety than “complex/fibrous carbs”—which never bodes well for a contest prep diet, where your calories are already low.

But how can some people get away with eating “cheat foods” and still get lean? And why do they want to? And is there a cost? Layne Norton, owner of BioLayne LLC, a PhD in nutritional sciences, and the man who popularized the recent resurgence of the IIFYM diet, is going to give thorough answers to these questions.

MI: How come you have chosen to be an advocate for the IIFYM diet over traditional meal plans?

Layne: When I give talks, I always have to put everything in context, so I talk about the hierarchy of what’s important. The number one thing (shown in research studies of people who are successful in fat loss and muscle building) is hard work and consistency over time. I used to be a coach who would tell people, “Eat these foods, and not these foods,” and what I found was that people can’t stick to it. They can stick to it for contest prep, but invariably, the blowout is coming. People rebound after a show. I found that a very easy fix to that was to not limit their food choices during prep, and just say, “If you want the cookie, it’s fine. Just fit it in to your macros for the day and make sure you get enough fibre.” This immediately increased compliance by 200 percent. As soon as you know you can’t have something, that’s all you can think about. I would rather have someone be 90 percent, 100 percent of the time, than be 100 percent, 70 percent of the time, and the other 30 percent they’re completely off.

MI: Why do you think the IIFYM caught on like wildfire with some populations, and yet others are so vehemently against it?

Layne: I think because people care more about being right than getting the right answer. When you get ego involved, it becomes very difficult. It’s almost a sanctimonious, “I’m a better person than you because I suffer more than you do.” I see competitors talking about how they should have won because of all the sacrifices they made. No, the person who looks best should win; it doesn’t matter how much you put into it. Yes, it’s admirable that you are willing to sacrifice time with your family, and completely disregard your friends in order to get ready for a show. I think it’s also the issue of “guru-ism.” For example, if I tell someone contest prep is about being consistent, tracking your macros, being diligent and taking a decent amount of time to get ready, people will wonder why they would hire me. It sounds too easy and simple. They think there has to be magic foods or formulas. I think people want to overcomplicate things because it makes them feel more knowledgeable. If I tell you I went to school for six years to get a PhD and what I’ve come back to is that you have to be consistent, you have to work hard, and you have to track, that just sounds silly to people. They want the secret, a shortcut to the physique they want. People think if they’ve sacrificed more, they deserve to do better. Traditional dieting is like suffering for the sake of suffering so you can brag to your friends about having suffered the most. Self-control is fatiguing. What you want is something that requires the least amount of willpower in order to get you where you want to go, because eventually that willpower source will be tested. We want to pick a system of dieting that will tax our willpower the least so that when other life stressors comes up, the immediate response is not to screw the diet.

MI: Do you think people in contest prep should be entitled to free reign over their calories, or should they keep a tight leash on their macros?

Layne: If I’m on “poverty macros” on contest prep, let’s say close to 60 to 70 grams of carbs a day, am I going to be able to afford to eat a Pop-Tart? No, because that’ll be my entire carb allotment for the day, and I’m not going to be able to get any fibre. So it’s self-regulating; as you get lower on intake, you’re going to pick more high-volume, fibre-dense foods just by default. But giving someone the choice takes that pressure off. IIFYM dieters don’t have cheat meals, because they can fit anything in their macros and don’t feel the need to get to that belly-busting state, because they’re not deprived of anything.

MI: What about the science behind “clean eating” versus “If It Fits Your Macros”?

Layne: There’s a 95 percent failure rate in the scientific literature for dieting studies, because their stipulation for success is having to lose weight and keep it off for two years. People can’t keep it off. Why? Because the type of diets people use are diets that tell them, “Eat this, not this.” The empirical data supports IIFYM. We’ve seen people who can get just as lean—if not leaner—using it. The science supports it because if you search on PubMed for “clean eating,” you won’t get any hits. There is no objective definition of “clean eating.” Every diet out there that people are comparing use macros. Saying you don’t do macros when you’re “eating clean” is like speaking and saying you don’t do the alphabet.

MI: What about the amount of sugar some people justify having on an IIFYM diet?

Layne: The glycemic index is only important in isolation. If you consume a carb with protein, fat, or fibre, it completely blunts the glycemic/glucose response, and it ends up being almost the exact same (that is, comparing a food like Pop-Tarts to broccoli). All those things will slow and delay gastric emptying to the point where it’s not that different. Bodybuilders tend to always eat fibre and protein with their meals, so it really doesn’t make a difference. All carbs break down into sugar. People don’t make a big deal when they see someone eating a lot of fruit. People who eat fruit tend to be stronger, live longer, but they’re eating a lot of fruit. But that’s because fruit has fibre associated with it. So it’s not a problem with the sugar itself; it’s a problem of people who eat a lot of sugar not eating a lot of fibre. You have to identify if there’s an actual mechanism at work.

As you can see from the above interview, an argument can be made for either side of this “traditional bro dieting” or IIFYM “flexible dieting” plan—it’s just a matter of personal preference. We can’t recommend one over the other, but we can recommend you try it out if you haven’t yet, and see what all the fuss is about!

  1. Holt, SH. A satiety index of common foods. National Center for Biotechnology Information. U.S. National Library of Medicine, Sept. 1995. Web. 22 July 2014.
  2. Rizkalla, SW. Glycemic index: Is it a predictor of metabolic and vascular disorders? Current Opinion in Clinical Nutrition & Metabolic Care. 17.7 (2014): 373-78. Web. 22 July 2014.
  3. Weickert, MO, Pfeiffer, AF. Metabolic effects of dietary fibre consumption and prevention of diabetes. Journal of Nutrition. 138.3 (2008): 439-42. National Center for Biotechnology Information. U.S. National Library of Medicine, Mar. 2008. Web. 24 July 2014.
  4. Lennerz, BS, Alsop DC, Holsen LM, et al. effects of dietary glycemic index on brain regions related to reward and craving in men. American Journal of Clinical Nutrition. 98.3 (2013): 641-47. Web. 24 July 2014.
  5. Ludwig, DS, Majzoub JA, Al-Zahrani A, et al. High glycemic index foods, overeating, and obesity. Pediatrics. 103.3 (1999): E26. Web. 24 July 2014.

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