"Calories in, calories out" is both true (in the thermodynamic sense) and accurate enough to be useful (in a practical sense). I've personally performed the experiment, using MyFitnessPal and a $14 digital scale, and it turns out that I can control my weight to within a few pounds.
There are a few caveats:
- Yes, your diet composition does have metabolic effects. Protein, sugar and fat all follow different metabolic pathways, and converting between them requires energy. Protein is supposedly easier to store as lean mass than as fat, for example. But unless you're already lean and training hard, these effects are relatively minor. If you want to lose 50 pounds of fat, calories are good approximation.
- Unless you're a hard-core distance athlete, the "calories out" side of the equation is mostly useless. Depending on your weight, walking a mile burns about 1 Oreo. Essentially, it takes a lot of energy to run your brain and your digestive system, but exercise is surprisingly energy efficient. So if you work at a desk job, and you don't run 5 miles a day, then use the "Sedentary" option when calculating your daily calories.
- If you want to be both lean and muscular, things get trickier, because you need to worry about your muscle:fat ratio. You can control this with resistance training. But weightlifting while losing fat can be pretty metabolically brutal. Conventional wisdom says that it helps to watch your protein:carbs:fat ratio, and to eat a nutrient-rich diet. (And my personal experience bears this out, especially once I've exhausted the easy gains in the weight room.)
- Most diets fail because most people stop dieting. If you revert to your old habits, you'll eventually revert to your old weight and body composition. As a general rule, few people stick with long-term lifestyle changes.
Losing weight and becoming muscular are both solved problems. The major challenge is sticking with the behaviors that produce the desired result.
An even blunter instrument that I’ve found very useful for weight and health is “mass in, mass out”.
That is, in a First Law sense, you can’t gain more than the mass of what you eat & drink, and you will always lose a certain amount of mass each day through breathing (metabolism, exercise) and excreting (waste, sweat).
So for example I lose 1–2 pounds a day with my metabolism, activity level, and diet, so I eat a bit more than that per day and try to make sure that those foods are healthy most of the time. For me, “healthy” means mostly plant-based, high in fiber, balanced in nutrients, and so on. I joke that my diet consists of vegan food and cheeseburgers, but it’s pretty close to the truth.
I think this should be the first step that most people take toward changing their dietary habits, because it’s dead simple: look at the weight on the package of the stuff you’re putting in your face, and get a cheap kitchen scale if you want to be particular about it. Then incorporate calories as you begin to get an intuitive sense of how caloric density affects the answer to “How much of this can I eat if I want to maintain/lose/gain weight?” and then incorporate other details like macronutrients.
Even before all this, the zeroth step is to document your habits by just writing them down. It might just be how my mind works, but if I want to fix something about what I’m doing—eating, sleeping, taking drugs—then it’s way easier to think about it in terms of adjusting a graph than all the details of the actual problem at hand.
Actually most diets fail because you stop dieting AND when you do, you now have decreased your metabolic rate and increased your production of hunger hormone. In summary you are way more likely to fail keeping a stable weight after dieting then you were before.
But that's the point. A diet is not something that you do a few months after which you get and keep a killer figure while returning to eating whatever you want. A diet should be the preliminary to a permanent shift in eating habits.
This is very true. We just need to avoid recommending unsustainable diets based on calories in/out thinking. Since they all ultimately fail. Also why settle for a decreased metabolic rate when you could actually increase it and enjoy the extra energy instead. No need to feel miserable the rest of your life.
There are a few caveats:
- Yes, your diet composition does have metabolic effects. Protein, sugar and fat all follow different metabolic pathways, and converting between them requires energy. Protein is supposedly easier to store as lean mass than as fat, for example. But unless you're already lean and training hard, these effects are relatively minor. If you want to lose 50 pounds of fat, calories are good approximation.
- Unless you're a hard-core distance athlete, the "calories out" side of the equation is mostly useless. Depending on your weight, walking a mile burns about 1 Oreo. Essentially, it takes a lot of energy to run your brain and your digestive system, but exercise is surprisingly energy efficient. So if you work at a desk job, and you don't run 5 miles a day, then use the "Sedentary" option when calculating your daily calories.
- If you want to be both lean and muscular, things get trickier, because you need to worry about your muscle:fat ratio. You can control this with resistance training. But weightlifting while losing fat can be pretty metabolically brutal. Conventional wisdom says that it helps to watch your protein:carbs:fat ratio, and to eat a nutrient-rich diet. (And my personal experience bears this out, especially once I've exhausted the easy gains in the weight room.)
- Most diets fail because most people stop dieting. If you revert to your old habits, you'll eventually revert to your old weight and body composition. As a general rule, few people stick with long-term lifestyle changes.
Losing weight and becoming muscular are both solved problems. The major challenge is sticking with the behaviors that produce the desired result.