Will Brink's Unified Theory of Nutrition

"A calorie is a calorie"
The old school of nutrition, which often includes most nutritionists, is a calorie is a calorie when it comes to gaining or losing weight. That weight loss or weight gain is strictly a matter of "calories in, calories out." Translated, if you "burn" more calories than you take in, you will lose weight regardless of the calorie source and if you eat more calories than you burn off each day, you will gain weight, regardless of the calorie source.

This long held and accepted view of nutrition is based on the fact that protein and carbs contain approx 4 calories per gram and fat approximately 9 calories per gram and the source of those calories matters not. They base this on the many studies that finds if one reduces calories by X number each day, weight loss is the result and so it goes if you add X number of calories above what you use each day for gaining weight.

However, the "calories in calories out" mantra fails to take into account modern research that finds that fats, carbs, and proteins have very different effects on the metabolism via countless pathways, such as their effects on hormones (e.g., insulin, leptin, glucagon, etc), effects on hunger and appetite, thermic effects (heat production), effects on uncoupling proteins (UCPs), and 1000 other effects that could be mentioned.

Even worse, this school of thought fails to take into account the fact that even within a macro nutrient, they too can have different effects on metabolism. This school of thought ignores the ever mounting volume of studies that have found diets with different macro nutrient ratios with identical calorie intakes have different effects on body composition, cholesterol levels, oxidative stress, etc. Translated, not only is the mantra "a calorie us a calorie" proven to be false, "all fats are created equal" or "protein is protein" is also incorrect. For example, we now know different fats (e.g. fish oils vs. saturated fats) have vastly different effects on metabolism and health in general, as we now know different carbohydrates have their own effects (e.g. high GI vs. low GI), as we know different proteins can have unique effects.

The "calories don't matter" school of thought
This school of thought will typically tell you that if you eat large amounts of some particular macro nutrient in their magic ratios, calories don't matter. For example, followers of ketogenic style diets that consist of high fat intakes and very low carbohydrate intakes (i.e., Atkins, etc.) often maintain calories don't matter in such a diet.

Others maintain if you eat very high protein intakes with very low fat and carbohydrate intakes, calories don't matter. Like the old school, this school fails to take into account the effects such diets have on various pathways and ignore the simple realities of human physiology, not to mention the laws of thermodynamics!

The reality is, although it's clear different macro nutrients in different amounts and ratios have different effects on weight loss, fat loss, and other metabolic effects, calories do matter. They always have and they always will. The data, and real world experience of millions of dieters, is quite clear on that reality.

The truth behind such diets is that they are often quite good at suppressing appetite and thus the person simply ends up eating fewer calories and losing weight. Also, the weight loss from such diets is often from water vs. fat, at least in the first few weeks. That's not to say people can't experience meaningful weight loss with some of these diets, but the effect comes from a reduction in calories vs. any magical effects often claimed by proponents of such diets.

Weight loss vs. fat loss!
This is where we get into the crux of the true debate and why the two schools of thought are not actually as far apart from one another as they appear to the untrained eye. What has become abundantly clear from the studies performed and real world evidence is that to lose weight we need to use more calories than we take in (via reducing calorie intake and or increasing exercise), but we know different diets have different effects on the metabolism, appetite, body composition, and other physiological variables...