by Mike Roussell, PhD T-Nation
Here's what you need to know...
The amount of carbs you can eat while still losing fat is directly related to your insulin sensitivity. As a lifter or athlete, yours should be good.
For many fit people, cutting carbs from 40% down to 20% of calories won't give them any additional fat loss benefit. So why do it?
Start your fat loss diet at 50% carbohydrate intake, then adjust down from there only if and when it's needed to keep the fat loss going.
Do not go by how you think you "feel." Go by the results you're actually getting.
Two people come to me for diet help. They both need to drop fat and improve their body composition. One is an out of shape 40-something stockbroker and the other is a fit movie star getting ready for an action movie. What should I do? Cut carbs right? For the longest time, fat loss diet advice has essentially been "eat less carbs." But it would seem ridiculous to give these two individuals the same diet advice, wouldn't it? Well, it is ridiculous, but that's what we've essentially been doing with the "eliminate carbs to lose fat" mantra.
At its most basic level, eating less carbs is good advice. Most people would benefit from eating fewer carbohydrates. But what we're discovering is that the level of carbohydrates that you can consume while still losing weight is directly related to your insulin sensitivity. More to this point, certain levels of carbohydrate restriction are unnecessary for individuals with good insulin sensitivity as it doesn't further enhance fat loss. So giving our stockbroker and movie star similar diets wouldn't make sense. Besides, everyone I know would like to eat as many carbs as possible and still reach their body comp goals. Wouldn't you?
The Impact of Insulin Sensitivity
Let's look at two different studies that have begun to explore carbohydrate cut points for eliciting maximum fat loss with respects to individual insulin sensitivity. In the first study, researchers wanted to look at the long term differences between a low fat diet (a "traditional" weight loss plan) and a low glycemic load diet with respects to changes in body composition. They found that after 18 months, regardless of the diet the participants were put on, they all experienced similar changes in body composition. Chalk that up as a win for the "a calorie is a calorie" crowd, right? Well, not so fast. In a secondary analysis of the data, the researchers separated study participants by insulin sensitivity. They found that the people with the worst insulin sensitivity had the best body composition changes on the low glycemic diet, and it didn't matter what diet the people with the best insulin sensitivity were put on they got just as lean either way.
In another study, the A to Z Study, researchers put people on one of four diets: Atkins, Zone, Ornish, or a control diet (the LEARN diet traditional low fat stuff). At the end of 12 months the people on the Atkins diet lost the most weight. Low carb rules! Again, not so fast. In a secondary analysis of this data, the researchers pitted the high (Ornish) and lowest (Atkins) carb diets against each other with respects to weight loss and study participants' insulin sensitivity. Just as in the previous study, people with the poorest insulin sensitivity lost more weight on the lower carb approach. People with the best insulin sensitivity lost the same amount of weight regardless of diet.
I'm a believer in the benefits of carbohydrate restriction, but I'm also a big believer in the fact that carbs are delicious. If cutting your carbs from 40% down to 20% of calories won't give you any additional fat loss benefit then why do it? Why not lose as much fat as you can with your carbs at 40% of calories and then reduce it after your fat loss begins to slow?
Exercise: The Missing Link from the Research
These two studies show that an individual's insulin sensitivity impacts the level of carbohydrates necessary to maximize fat loss. But in all these studies, exercise wasn't part of the fat loss strategy. Exercise itself increases muscular insulin sensitivity. This increases the amount of carbohydrates you can consume and shunt towards your muscles automatically. It's also important to note that the carbs that you cram into your muscles post-training stay there as your muscles don't have the enzymatic machinery necessary to release sugar from glycogen to the rest of your body.
As a T Nation reader your insulin sensitivity should be better than most, so you'll find yourself in a place where you can lose just as much fat with a higher carbohydrate intake. Starting your body composition training with a higher overall carb count will give you greater flexibility later in your diet to reduce carbs when calories are at a premium.
What To Do
Don't start any body comp diet phase with your carbohydrates any lower than 40% of your total calories, then adjust from there. You may be wondering how much higher you can start since the A to Z study used the Ornish diet, which is upwards of 65% calories from carbohydrates. You can go higher, but 50% of calories from carbs is probably the max you'll want to go as it's important to remember that everything in your diet is connected.
As you eat more carbohydrates you'll need to eat less of something else (assuming that total calories is capped at a specific level since you're in a fat loss phase). You'll want to keep your protein intake at 30% of your calories and never lower than 1.6g/kg body weight. The rest of your calories will come from fat, which in this case is the remaining 20% of calories. So at the high end of your carb intake, your diet will look like this:
Let's put some more numbers to that:
Wait, that's a low-fat diet! What? Let's pause here. I'm not some crazy PhD keyboard jockey recommending a low-fat diet. This won't work for everyone. But if you're looking to lose as much fat as possible while eating as many carbohydrates as possible and you have good insulin sensitivity, this is how you should start.
The one thing you might be concerned about with this higher carbohydrate/lower fat approach is satiety or feeling full. With only 20% of your calories from fat, will you be satiated enough? No one likes to feel like they're starving just after they finish a meal. But satiety shouldn't be a problem as long as you're eating ample vegetables as part of your 50% carbohydrate intake. Here's how:
Vegetables Eat them, especially high-fiber green ones and high volume veggies that weigh a lot but don't contain a lot of calories. You body senses how much a food weighs more than it does the calorie content of the food. Eating more vegetables is always linked to eating less calories and greater feelings of fullness.
Insulin While it's often talked about as the devil when it comes to fat loss, most people don't realize that insulin is a satiety hormone. So the increase in carbohydrates will lead to a hormonal cascade that leads to increase satiety.
Protein Protein is linked to increased fullness via multiple mechanisms in your body, from signals in your digestive tract to modifications in your brain. 30% of calories from protein will give you the lean body mass protection that you need as well as the fat loss/satiety benefits.
So satiety shouldn't be an issue. But if you find that it is, no problem, just drop your carbohydrate intake by 5-10% and adjust your fat intake according. Your new starting point would be:
Forget How You Feel!
Don't just eat carbohydrates recklessly and then get upset when your body composition isn't improving. Don't blow this idea off because it doesn't "feel" right and carbs make you "feel" fat. Optimizing body composition is less about how you feel and more about how your body changes.
It drives me crazy when people say they "feel leaner." You either are leaner or you aren't leaner; it doesn't matter how you feel about it. Treat your body like a science experiment. Put the plan into action and measure how your body responds. Make adjustments to your diet based on how your body has responded, not how you feel about your body's response. Your newly visible abs will thank you.