The conventional view of dieting and weightloss is calories in = calories out. People (especially geeks like me) love to cite the first law of thermodynamics: energy can neither be created or destroyed. Hey, that’s great — but humans aren’t closed systems or bomb calorimeters. The digestive system is complex, and the thousands of compounds that reach our bloodstream are then managed by an equally complex array of hormones, vitamins, anti-oxidants, immune cells, carriers, receptors, and more. The idea that the complexity of the human body can be neatly summed up into the simple phrase “calories in = calories out” is silly. As appealing as it is to dress up the phrase with an appeal to scientificalityness, it misses the important role that hormones (et al) have.

But I won’t talk about them per se. Instead, my point today is to say that when you eat carbs matters more than how much you eat. Carbs (whether sugars or starches) quickly convert to blood sugar. Excess blood sugar causes your pancreas to produce insulin, which then shuttles that sugar off into adipocytes (fat cells). But there’s a trick here between the conversion and insulin production; I said excess blood sugar.

When you’re fasting, you burn off the glycogen stored in muscles and your liver. The brain has a constant demand for glucose and if you’re not eating, it has to get it from somewhere. The major source is liver glycogen (muscle glycogen can not move out of muscle cells; it can only be used locally), and if your glycogen stores are depleted, your body wants to restore them. Consuming carbs when fasted, therefore, won’t increase body fat as much as it would right after a meal.

So here’s my point: The same calories consumed at different times can have different effects. Don’t eat dessert right after dinner. If you’ve got bad cravings for sweet things, consume them after fasting (whether that means at breakfast or after an all-day fast).

Of course, avoiding trouble carbs like fructose, alcohol, and grains is better than consuming them — but if you’re working on improving your diet, and need to take steps, the first thing I recommend is changing when you eat those carbs. You’ll start getting your insulin under control, and that makes it easier and easier to remove carbs altogether.