In the last couple of weeks I’ve talked a lot about carbs and how our body reacts (or doesn’t) to them depending on the time of day or more accurately how long we’ve gone without them. Today we will continue on with the trend of carbs, this time taking a look at just how big of a difference the different types of carbs really matter what it comes to body composition. Everyone knows you should only eat complex carbs and not simple carbs, right? Certainly all simple carbs are stored directly as fat. Just Google it, there is no doubt about it.
I hope you detected the sarcasm in that last statement, because I was laying it on pretty thick. To get a fair argument what we really need is research that uses similar macronutrient protocols. Meaning the study needs to be consistent, something many studies lack because they don’t control intake of other macros or don’t control how much is eaten overall. Research can get tricky like that. Luckily I was able to track down some pretty solid research that looked into just what we’re looking for.
In a study done by Saris et al. (2000) 398 moderately obese adults were assigned to either a low-fat high simple carb group, a low-fat high complex carb group or a control group. The study went for a total of 6 months and changes in body weight, body composition and blood lipids were measured. At the end of the study there was no significant difference in body weight, body composition or blood lipids between the simple carb group and complex carb group while the control group gained weight. (1)
That may be a pretty shocking result, but simple carbs vs complex carbs is a pretty loose term. One ranking often used is the glycemic index (GI) which is a ranking of carbs on a scale based on how they raise blood sugar after consumption. The lower the GI ranking the slower it is digested and absorbed thus producing a gradual rise in blood sugar and insulin levels while the higher the rating the faster it is digested and absorbed and in turn faster rises in blood sugar and insulin levels. Based on this it is generally considered best to eat mostly low GI foods and avoid high GI foods.
Research published in The American Journal of Clinical Nutrition in 2004 looked at the role of GI on body weight, body composition and risk factors for type 2 diabetes and ischemic heart disease in overweight healthy adults. During the 10 week study they split participants into two groups, giving them either high GI or low GI test foods. They matched total energy, energy density, dietary fiber and macronutrient composition. At the end of the study the results showed no significant difference in muscle retention or fat loss and it also didn’t affect blood pressure, heart rate, glucose and insulin metabolism or blood lipids and there was even no difference in perceived hunger between the groups. The only difference came with a higher decrease in LDL cholesterol in the low GI group. (2)
A similar study published in the International Journal of Obesity investigated if a diet with a reduced GI had effects on appetite, energy intake, body weight and body composition in overweight and obese women. This crossover study had two consecutive 12 week periods in which low GI foods were replaced with high GI foods, matching macronutrient composition, fiber content and energy density. Once again there was no difference in energy intake, body weight or body composition nor was there a difference in ratings of perceived hunger or fullness. (3)
One thing we don’t know is the exact foods participants were eating in this or how big of a difference there really was in the GI ratings of the foods, but either way it shows it’s entirely possible to change body composition in a similar matter without overly stressing about simple or complex carbs. I’m not suggesting GI values mean nothing, but I am questioning the increased awareness that seems to be out there to completely avoid all high GI foods in your diet.
The other thing that comes to mind is if it matters what your starting point is when trying to change body composition. In a meta-analysis looking at the relations between GI properties and health outcomes it was noted that a diet higher in low GI foods are better for you if you start off unhealthy, but in those who are already healthy there appears to be little to no effect. Therefor those of us who have been into health and fitness for a longer period of time and are already healthy may be able to get away with more high GI foods without adverse effects. (4)
Okay by now I think you get my point. There seems to be good support to show that perhaps high GI / low GI or simple carbs vs complex carbs don’t make a big difference as long as you hit the numbers required for your diet. Now don’t think you can just run out and eat anything you want without any negative consequences. While I’m not saying sugar is a good thing and to eat a lot of, I am saying you can probably eat more sugar than you may think without it hurting your progress. I’m also not suggesting you eat mostly simple carbs, but I am a proponent of not excluding them from your diet and incorporating a more flexible sustainable long-term diet, something we will be talking about in the coming weeks. There is one thing that really stuck out to me about all these studies that may explain why there was no difference in results. That key factor is what we will be talking about next week when we return.