Layne Norton popularized the flexible diet, also known as 'If It Fits Your Macros' (IIFYM). The idea here is in the name of the diet itself; eat whatever you like, as long as it fits your macronutrient requirements.
Every calorie that you eat comes from one of three macronutrients: protein, carbs, or fat. If you want to lose weight, all you need to do is burn more calories than you eat. But how do you burn calories? We usually think of burning calories through exercise, but our we use the majority of the calories we consume for regular bodily functions. One thing that we rarely consider is that digesting food itself requires calories. Each of these macronutrients has a different caloric requirement for digestion.
Layne says that of the three macronutrients, "Protein has a higher thermic effect than carbohydrates and fat. So we know that higher protein diets cause more weight loss and better lean body mass retention." Through this logic, Layne concludes that as long as eat the right amount of protein and calories, you can eat carbs and fat in any ratio and from whichever sources you prefer. This means that anything from pizza to ice cream to Doritos to Poptarts is on the menu for a flexible a diet.
The theory of the flexible diet allows you to eat whatever you want because the hypothesis is that foods we consider unhealthy are only harmful if we eat them in a caloric surplus. Sugar isn't bad because it makes you fat, it's bad because if unchecked, it causes you to overeat. However, if you monitor your calorie and macronutrient consumption, limiting your calories and controlling your protein, then a can of coke is no less healthy than a sweet potato. This is because the benefits of weight loss come primarily from calorie restriction and losing weight is the best way to improve your health.
After following a Ketogenic diet for the past three weeks, I learned that eating 3800 calories and 250 grams of protein per day allowed me to lose two pounds. Now, I am going to try a flexible diet, eating the same 3800 calories and 250 grams of protein but instead of restricting myself to 20 grams of carbs as I did on a Ketogenic diet, I will eat whatever else I want to get the rest of the calories that I need.
I am curious, can I get the same advantages that I received from a ketogenic diet while indulging in foods that the keto diet banished? If you are interested in learning whether this can be an effective strategy for your weight loss, then follow along and I will keep you updated.