How long do carbs stay in the body before they turn into fat?

PFA Client: I have a question for you. Everything I read seems to suggest that everything you eat (carbs, protein, fat) eventually turns into fat and is used for energy. However, I have also read that when you go into anaerobic exercise, the energy comes from carbs.

My question is how long do carbs stay in the body before they turn into fat? In other words, if I eat carbs 12 hours before working out, will they be available to convert to energy, or do they need to be eaten closer to workout, and does it matter if they are simple or complex carbs for this purpose?

Doug Jackson: Good questions, but try not to over-analyze this stuff.

Some of the best writers write with theory that just doesn't match real-world results.

Regarding the protein, carbs, and fat being stored as fat, this is a complex issue, but in general, they will only be stored as fat if your calorie intake is greater than your calorie output throughout the day. In addition, the statement about anaerobic energy coming primarily from carbohydrates is true.

Regarding your question about carbs converting to fat, I want you to focus on the quantity and quality of carbs first and the timing second.

I like to make the analogy of your carb stores being somewhat like fuel in your own personal gas tank. Carbs are stored as fat if they are continually consumed after your carb stores are filled, just like gas would spill out of a gas tank after the gas tank is full.

In general, for fat loss, I suggest aiming to keep your carb stores (your gas tank) below half full most of the time. This will promote a hormonal and blood sugar state that is more supportive of fat loss.

Regarding carbohydrate timing, it may very well make sense to try to keep carbs low on days that you aren't particularly active. Further, there are sports nutritionist that I respect who suggest focusing the majority of your carbs within a few hours before or after your strength training workouts. The pre-workout carbs should allow you to have optimal fuel to train hard. The post-workout carbs help the body re-fuel and promote recovery and muscle tissue repair after the workout.

Regarding simple verses complex carbs, there's still a lot of confusion with issues like glycemic index and glycemic load coming into play. However, the general rule for fat loss is that simple carbs should only be consumed immediately pre-workout or immediately post-workout.

As I touched on in the article I did about nutrition paradigms, there are very different generally held thought processes when it comes to fat loss and workout performance. And the reality is that it's very tough to train hard and keep your strength levels up when you are on a fat loss diet. Because of this, I think it makes good sense with someone with your goals to eat for fat loss the majority of the day, but switch gears and eat for workout performance during the couple hours that are pre-strength workout period and eat for recovery during the couple hours post-strength workout.

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