Last week in my ongoing series of everything carbs, we looked at research that showed diets containing high GI carbs had the same results in body composition as diets structured around low GI carbs. I mentioned at the end of the article that I noticed something in the majority of the research that would explain why the studies had similar results. Today we will delve into that very reason. In fact, I can sum it up in just one word. Fiber.
Okay, end of article, that’s all you need to know! No? Okay, I’ll go into more detail. Yes if you were watching closely last week you could notice they were always matching total fiber in the diets of the subjects. High GI, low GI, complex carbs, simple carbs, no matter what they compared they always matched fiber and at the end of the study the results were the same. So why would it be that fiber would make that big of a difference?
Fiber is very thermogenic, in fact almost as thermogenic as protein. Fiber will help slow down any sugar or fast digesting carbs consumed. Dietary fiber is not absorbed the same as a typical carb as it is fermented by the intestines to short chain fatty acids and then absorbed. Meaning it doesn’t affect blood sugar because you absorb the energy as short chain fatty acids instead of glucose. This is why a diet high in sugary snacks is not the same as a diet high in fruit, even though in macronutrients they are similar. Sugary snacks have no fiber while fruit does. Fiber has much less metabolizable energy than do starchy carbs and the amount of energy extracted from fiber is less than other carbs. This is possibly because dietary fiber can decrease the transit time of food in the intestine and in turn result in less time for digestion and absorption. (1)
A nutrition review done by Howarth et al. looked at published studies on the effects of dietary fiber on hunger, satiety, energy intake and body composition in healthy individuals. Taken straight from the review “Under conditions of fixed energy intake, the majority of studies indicate that an increase in either soluble or insoluble fiber intake increases postmeal satiety and decreases subsequent hunger. When energy intake is ad libitum (at liberty,) mean values for published studies indicate that consumption of an additional 14 g/day fiber for >2 days is associated with a 10% decrease in energy intake and body weight loss of 1.9 kg over 3.8 months.” (2) Basically more fiber = less hunger and a greater amount of fat loss.
While sugar may not be a good thing, it’s not necessarily the prime culprit in fat gain like we are led to believe by today’s media. Research is starting to show it’s not necessarily the sugar that’s the problem, it’s the lack of fiber in those sugary snacks that’s the problem. That and of course that people are eating more calories than they are burning on a consistent basis, but it’s certainly not all from sugar. Of course sugar plays a role, but that doesn’t mean no sugar can ever be consumed.
GI only really matters if you eat carbs without protein or fat, which is why low GI in that case is better but even then it’s likely because of the fiber most low GI foods have which helps slow down the digestion. Personally I don’t find the glycemic index to be that valuable of a tool, at least not in the bodybuilding world.
Of course just because fiber is helpful for a smaller net energy gain and a key component of a healthy diet, that doesn’t mean you can eat as much as you want as long as you are eating a lot of fiber. It doesn’t matter what you eat, if you consume more calories than you burn you will gain weight. But if you are eating a lot of fiber it will be more difficult to over-consume due to the satiety that comes along with high fiber.
What’s the main point of all of this you ask? Well besides the fact that science is cool and I enjoy learning how the body works, the point is you don’t need to be perfect to reach your goals. If you are eating 400 grams of carbs per day and you eat 45 grams of fiber, I don’t think having one “bad” food that is high in sugar is going to hurt your results, just as the research I’ve shown you would suggest. However if you are only eating 150 grams of carbs per day and you eat a sugary snack with 60 grams of carbs, well that’s going to make it a lot more difficult.
Women should aim for 20-40 grams of fiber per day while men should aim for 30-50 grams per day depending on your caloric needs based on your current goals. Besides the benefits to your weight and body composition diets high in dietary fiber appear to significantly reduce the risk of developing coronary heart disease, stroke, hypertension, diabetes, gastrointestinal diseases and high cholesterol as well as, well you know, staying regular. (3)
Feel free to have some white rice over brown rice or regular pasta over whole wheat pasta. The macronutrients in them are the same with the only difference being fiber. “But you just said that fiber is the important factor Colin!” You’re right I did and fiber is important. However, as long as you are getting enough fiber from other sources throughout the day, it won’t make a difference. Even without the fiber the difference is likely to be minimal if you are hitting your macronutrient needs, but you’re certainly better off getting plenty of fiber.
I hope you’ll come back next week as I wrap this series up with a basic eating strategy to put everything we’ve been talking about together.
Join our list
Subscribe to our mailing list and get interesting stuff and updates to your email inbox.