Glycemic Index and Fat Loss: It Doesn’t Matter

As you probably have figured out by now, I’m a huge fan of dietary freedom as long as it brings you closer to your goals. I’m also quick to whip out some flaming Nunchucks in order to lay the smack down on any dogmatic method or gimmick that stands in the way of said goals. In many fitness circles the Glycemic Index is viewed as the magic bullet that makes fat loss possible, but I say this viewpoint is pure is hogwash.

But first things first, what is the Glycemic Index? It was created in 1981 by Dr. David Jenkins as a way of helping people with diabetes manage their blood sugar levels, and this concept has been carried over to the fitness industry within the last decade. The idea behind this is that low GI foods digest more slowly and thus keep blood sugar levels in check, helping keep the hunger beast at bay. Subsequently, higher GI foods are thought to send your blood sugar levels through the roof, only to come crashing down faster than a 1990’s Mike Tyson knockout.

This may sound all nice and dandy, but in terms of fat loss, why does it matter? Answer: It doesn’t for several reasons.

1. Taken out of context

In the case of the Glycemic Index, you have a tool that was created to help people with an actual health issue (diabetes) control their blood sugar, that is now being marketed towards people with no actual health issues as a way to lose fat. When you take the index out of its original context and apply to another vastly different situation, it ceases to become applicable, especially when you consider that the GI of a food is determined by eating it in isolation and after an overnight fast, both of which are not reflective of how we eat on a daily basis. Throwing in the fact that you can raise or lower the GI of a food by adding other foods to the meal doesn’t help make things anymore reliable, either.

3. Not supported by scientific evidence

A 2008 study out of the University of Cambridge compared a group who consumed mainly high GI foods to one that consumed mainly low GI foods. The result? That the GI of a food had no effect on body weight whatsoever. There are several diet books on the market that point to the Glycemic Index as the engine behind their results, when in reality the only magic happening is that many of the lower GI foods also tend to be lower in calories, which helps in creating a caloric deficit, which in turn drives fat loss. As a general rule of thumb, whenever a diet plan or system focuses on one food group to show you that this is the reason why their plan is superior to all others,  it is pure hype and they’ve simply managed to come up with a way of convincing you to eat less than you need to on a consistent enough basis to see results. All these roads lead to the same place in the end.

3. It makes things more complicated than they need to be

One thing that I’ve noticed above all else when I talk to people about nutrition is this: they’re confused as all hell, and with such a plethora of conflicting diet information available on the internet and in bookstores, I don’t blame them. You can eat this food but not that food, or you can eat both foods but only at breakfast, and if you for some reason disregard this advice and eat both foods together after 12pm, your dog will be kidnapped and the money in your savings account will be converted to lima beans – and you hate lima beans! This is a huge problem because this categorization of “good and bad”  leads to more unnecessary food discrimination that is the major source of all the confusion in the first place.

Imagine this scenario. You’ve had some issues with losing fat in the past due to confusion about what to eat, but now you’ve finally figured out a way to eat that is in line with your goals and you are experiencing much success – sweet. You get to talking about your newfound awesomeness to a friend whose opinion you respect greatly, and he tells you that while you’re losing fat now, it is simply a fluke and that your results aren’t “official” because you’re eating high GI foods. Because you respect this person so much, you abandon what was clearly working for you and start following their advice, and your fat loss stalls as a result.

You see what happened there? Well intentioned but crappy advice was given, and this already confused person who thought they were doing great by eating some watermelon and beets instead of a Big Mac was told that their food choices suck because because they both don’t follow some nonsensical rule. Now they’re more confused than they were before, and instead of this tool actually helping them, they have to deal with the cognitive dissonance of having their favorite foods labeled as subpar. Trust me, I know a woman who loves beets with all her soul and I pitty the fool who tries to tell her that they are anything but heaven on Earth.

The take home point is that you don’t have to complicate your life with any of this nonsense if you’re healthy, active, and simply want to look good. Cut the jibba jabba and stick to the basics of eating mainly whole & unprocessed foods and creating a caloric deficit through diet and training and you’ll be well on your way to achieving maximum sexy.

Photo Credit: WorldIslandInfo

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  1. says

    Just curious on your thoughts on the timing of high glycemic vs. lower glycemic foods. I have always tried to eat higher glycemic foods close to training and lower glycemic earlier in the day. I read nutrient timing back in college and have always eaten that way. When I want something I eat it though.

    As far as fatloss, I agree almost 100% but each person/client reacts differently to different diets. I stick to the basics with my clients and teach calories in/calories out. KISS right?

    Great blog as well man.

    • says

      Hey Steve,

      Thanks for stopping by.

      Yeah, I agree with you and try to keep it as simple as possible. Getting caught up in high GI vs low GI adds another level of complication to an issue that is already complicated enough for most people. As far as timing goes, especially when in a caloric deficit, the timing doesn’t matter all that much in terms of results. In general though, as you’ve said, it’s best to get your carbs in around your training session where they will be tolerated better and you can take advantage of nutrient partitioning.

      Unless you’re an athlete training to glycogen depletion and have to compete again shortly after, GI isn’t so much a concern, but more of how many carbs you can comfortably get in from the food source (I.E. it’s much easier to take in a large amount carbs post training via potatoes and pasta than it is vegetables).

  2. Nancy C. says

    It’s amazing how many ways people try to get around the basics of just stop eating so damn much.

    • says

      For realio. I think, in all honesty, that some people like looking for new possible solutions that are more complicated and thus give them the illusion that they are working towards their goal.

  3. Andrew says

    Good one Roger.

    I think people rely far too heavily on making qualitative changes to their diet rather quantitative ones. While striving to consume more whole, unprocessed foods is a great idea, and something most people should do for a variety of reasons, do not think it will magically enable you to lose weight/fat.

    • says


      What would you do if you needed to come up with cash in order fund a trip to Brazil? Making qualitative changes to what you buy might help for sure, but you’d get there so much faster by making quantitative changes, aka watching that money like a hawk, cutting back spending/increase income and saving more. The body is the same way.


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