At @T3hPwnisher nails it, as he often does. It’s not about percentage of totals.
Consider this example: you’re dieting to lose body fat. Your protein is 175g daily (or whatever) and 40% of your total calories. As you have to adjust calories down and feel crappier, you are at an increased risk of losing muscle. At the same time, that 175g becomes 50% of your daily calories. Would you adjust protein down, when at your highest risk of muscle-wasting, to stay on ratio? Surely not.
It’s typically a better bet to set your calories as a multiple of body weight, protein as a multiple of body weight (or lean body mass if over day 20% body fat), fat minimum as a multiple of body weight/ fat, and then spread the rest of your calories between carbs/ fat as preferred. You’re going to have to adjust as you go, anyway, so it doesn’t have to be exact.
Here’s an example for someone 200 lbs, ~12-15% body fat (basically in athletic condition), who wants to lose 1-2 lbs a week while improving gym performance. I’m only going to demonstrate caloric starting points/ general adjustments; you can also consider additional cardio a tool to create deficit, but I think that gets tricky.
- We’ll start at 13 kcal per lbs. We’re cool to lose slowly, so we’ll start at the higher end of where we could expect a drop. I do some risk in adjustments that are too minute, but probably not for us in this situation.
- We’ll set protein at 1g per lbs. In reality, you can get crazy on this and justify anything between .72 - 1.25, but let’s pick some easy middle ground. We’re not mathematicians here.
- We’re going to set our fat baseline at .4g per lbs.
- In this example, we’ll make the rest carbs. You don’t have to - distribute the remainder between carbs and fat as you wish. You’ll see why carb-heavy is easier for adjustment in a sec, but most important is to see what foods you’ll actually want to eat and do it that way. I travel for work and find it more frustrating to try to stay low-carb than low-fat.
So that gives us:
- 200 lbs. x 13kcal = 2600 daily kcal
- 200 lbs. x 1g protein = 200g protein daily
- 200 lbs. x .4g fat = 80g fat
- 2600 kcal - 800 from protein (200 x 4) - 720 from fat (80 x 9) = 1080 kcal remaining
- 1080 kcal / 4 = 270 carbs daily
Our starting point then is 200p/ 270c/ 80f.
Now, if we don’t lose 1-2 lbs. per week, we have to adjust. I’d recommend 10-15% adjustments, depending on how bad the week was. Since we set our fat at the baseline, we’ll just adjust carbs (that’s where I said it was easy!). We won’t touch protein or fat because we were on the low-ish end anyway and we don’t want to diet more than 16 weeks straight where we might see big enough body weight/ composition changes to warrant a new baselining.
So we only lost .5 lbs. Not awful, but we’ll adjust. Since we lost something, let’s say we’ll drop 10%.
- We were at 2600 kcal, so 2600 x .1= 260
- 260 / 4 = 65 carbs
- 270 carbs (starting point) - 65 = 205g carbs
- So our next week is 2340kcal with 200p/ 205c/ 80f
Rinse and repeat!