In past years, I learned a lot about diet & fitness. There are many personal & psychological aspects to this, but there is also some hard science.
Changing the physical form of your body is a very powerful tool for self-improvement, but there is also a lot of harmful information out there. I want to attempt to strip it down to some basic scientific principles to explain how the process works, and present guidelines. You will find no magic diets, “superfoods” or special tricks here. This is a blueprint for how to treat your body as the biological machine that it is, and make it change in any way you like.
The title was a bit of bait and switch. For people who want to lose weight, the actual goal is to lose fat. Losing muscle, water, and bone density will all make the scale go down but is not good for you. Similarly, for people who want to gain weight, it is far better to gain muscle and a bit of fat specifically. Familiarize yourself with the difference between lean body mass and total weight.
- To lose fat, you must eat fewer calories than you expend (“caloric deficit”), to gain weight, you must eat more (“caloric surplus”). Calories are the building blocks.
- Macronutrients are important, and come in 3 categories: protein, fats, and carbohydrates. You need all three at all times, and it is a balance game.
- No macronutrient or food is evil. This is not about fad dieting or choosing “angels and demons” in the food world. Beware and avoid any diet that preaches extreme restriction on any of the 3. This is about fuel for your body. There are however certain choices that align with our goals, and others that don’t.
- Avoiding muscle loss (sarcopenia) in the process means ensuring you have enough protein, because protein specifically acts as building material for muscle. And so we’ll index the way we eat off of protein.
- To know how much your body needs, use a Total Daily Energy Expenditure (TDEE) calculator. These never give you exact results, but they get you into the ballpark and you can adjust with experimentation
How much of a Deficit or Surplus?
Generally, 10-15% is best. There is no particular magic to this number, and there is a tradeoff between speed and your ability to comply with a plan. If you eat 85% of your TDEE, you will steadily lose weight, something close to 1% of bodyweight per week. If you eat 70% or less of your TDEE, you will lose weight much faster, but you will be hungry all of the time, and you may not have enough calories in your “budget” to eat a healthy diet. Similarly, if you eat 200% of your TDEE, you may feel like you’re cramming food all day long, and because muscle can’t grow but so fast, even if you are working out all the time you will be gaining mostly body fat.
Slow and steady wins the race.
How to Assemble a Plan
To figure out what to eat to get this done, we have to have some facts about how food works. Then we have to use those facts to pick some targets. Taken together, those targets will become our plan.
Check it out! This means that a morsel of fat is more than double the number of calories as the same weight of rice. This will be important.
Now we need some targets. Remember we start with protein as our primary target, because preserving and growing muscle is a key priority when changing your body.
- Protein: you need to pick this first. Based on your body weight, you can choose from the table below
- Fat: generally it is good to limit this to 15-20% of your total daily calories. In the fact table above, you’ll see fat is 9 calories per gram. So we go low fat because it doesn’t take much food to get to a lot of calories.
- Carbohydrates: this will be chosen for us. If we know how many grams/calories of protein we need, and we also know how much fat, and we also know the total caloric goal we’re shooting for — then it’s just an algebra problem and you can solve for the number of carbs you will get.
Theory is nice, but it’s much easier to see this stuff in practice when you do some math and assemble it all together. So that’s what we’ll do next. Make a spreadsheet or just use paper and pencil to follow along, substituting your own information.
A Worked Example
- 6 foot tall male weighing 210 pounds, with a goal of losing weight.
- Using the TDEE calculator, this is what that body needs:
What’s the caloric goal? Well, he’s trying to lose weight. So he needs a caloric deficit. Let’s say he eats 85% of his TDEE (refer back to the principles above). That is 2,311 * 0.85 = 1,964 calories per day. If he does that, he can expect to lose about 1% a week. At 210 pounds, that’s an average of 2.1 lbs of body fat loss per week.
In the Bulking/Cutting table above, he needs 0.75g of protein per pound bodyweight. That means he’ll need 210 * 0.75 = 158g of protein per day. This is a bit on the low side, he could go up to 1.5g of protein per pound, but this will work for now.
How much protein? We know that protein is 4 calories / gram. So 158g protein * 4 cal/g = 632 calories a day from protein.
How much fat? We want to target 15% of daily calories, so that’s simple: 1,964 calories/day target * 0.15 = 295 calories/day from fat. Since we know that fat is 9cal/g, we can calculate 295 / 9 = 33g of fat per day.
How much carbohydrates? This is where we “solve for carbohydrates” because we already know the other two terms.
- Our target is 1,964 calories/day
- 632 of those are protein
- 295 of those are fat
- So carbohydrates must be 1,037 calories. Dividing by 4 calories/gram, you get 259g of carbohydrates.
If you were to make a pie chart of this, you’d see that this is a relatively balanced diet that doesn’t crowd the diet full of one thing or another.
After following that math above, we end up with:
- Protein: 158g/day = 632 calories
- Fat: 33g/day = 295 calories
- Carbohydrates: 259g/day = 1,037 calories
Remember: none of this is set in stone. You can play with the percentages all you like; add protein, maybe add a bit of fat. If you do that, carbohydrates will have to come down and that’s fine. The main principle to keep in mind is that protein has to hit a minimum, otherwise this man risks losing as much muscle as fat in the cutting process.
Exercise is a great idea. It keeps your heart & body healthy. Without it, you can’t build new muscle really, you can only aspire not to lose what you’ve got. It burns extra calories, so if you eat 85% of your TDEE then you can create an even larger deficit.
But exercise is not strictly necessary for weight loss or weight gain: the balance of energy in the body (calories in/calories out) is enough to get the job done. All of that said, exercise is like a hammer: you can drive nails without it, but your life will be way, way easier if you use the right tools.
A few principles may help when selecting and pursuing exercise:
- You don’t need to overdo it to see good results. 20-30 minutes 3-4 times a week is plenty.
- Try to make it social. Social accountability is a key way people stick to things. Walking with friends, playing soccer, try to incorporate a social element if you can.
- Fun matters. Remember riding your bike as a kid? It’s so much fun. You were exercising then. Did you think of it as exercising? Probably not. There’s a lesson in there.
- If you want to gain weight & muscle, your best bet is to do compound weight lifting a few times a week.
Building a Menu & Sticking To It
This is not something we’ll cover in this post, because I am not a cook or a diet guru looking to sell anything. Your food choices are yours alone, I’d like to instead stick to some key principles you should keep in mind when choosing:
- Slow and steady wins the race: if your plan is to gain/lose 1% a week, it will take some time. So make sure you make choices you can comply with over weeks. If your diet is full of foods that you hate, you will fail.
- How you feel matters a lot. If your diet makes you feel like you’re starving all the time past the first few days, you will probably fail. So consider spreading out and adjusting your meal times to optimize for your mood. If you ignore how you feel, you will have compliance problems.
- Measure everything. All of this math means nothing if you don’t know what you’re actually eating. Buy a digital scale. Weigh things. Prepare your meals ahead of time. A corollary of this is that restaurants are not your friend if you are trying to make a change. Usually you won’t have any control or ability to measure portion, which means you won’t know what you’re taking in, which means your plan may not work, even if you try to stick to it.