How do you know how many calories you should be eating per day?
The Short Answer (The Long Answer is below)
*I am not a health professional. Use common sense. If you have a health condition, please consult your doctor.
Estimate how many calories you need in order to remain the same weight.
In order to lose weight you will need to eat fewer calories than you burn. You can start at a 20% deficit. Take the amount of calories you need to remain the same weight and multiply it by .8 to get how many you should eat in a deficit. Monitor your weight loss and overall health, and adjust as necessary until you hit your goal.
In order to build muscle you will need to eat more calories than you burn and you will need to do resistance training. Take the calories you need to remain the same weight and multiply that by 1.2. This puts you in a 20% surplus. Monitor your weight and overall health, and adjust as necessary until you reach your goal.
The Long Answer
First, we need an estimate of your TDEE (Total Daily Energy Expenditure). This is how many calories you need to eat per day to remain the same weight. The best way to do this is to accurately track your calories and weight. There are a bunch of TDEE calculators available online. Of course, none of them will be as accurate as you tracking your intake. If you don’t know for now, don’t sweat it. Most of us aren’t.
A good way to figure it out is the Katch-McArdle Equation. This estimates your Basal Metabolic Rate based on how much lean tissue you have. Basal Metabolic Rate (BMR) is the number of calories your body would burn if you did absolutely nothing all day long but lay on your couch. Lean Body Mass (LBM) is weight minus body fat. We take this number and apply a multiplier to account for how active you are to determine your Total Daily Energy Expenditure (TDEE).
BMR = 370 + (21.6 x LBM in kg)
LBM = weight in kg x (1 – (body fat percentage as a decimal))
Body fat percentage as a decimal may sound complicated but it isn’t. For instance, for someone who is 20% body fat, that would be expressed as .20. For someone 15%, it would be .15. There’s no way to exactly determine body fat on a living creature, so you’ll have to estimate. Don’t worry, it’s really okay. You can do this by comparing yourself to pictures. (Google is our friend!) It will be an estimate but it should be fairly accurate. There are also calculators to convert lbs. to kg, but if you want to do it yourself, just multiply your weight in lbs. by .45.
Your BMR represents about 55-75% of your TDEE. If you’re less active, it will be on the higher end. If you’re more active, it will be on the lower side.
The activity multiplier will account for this.
If you’re not very active, use 1.3. If you are very active (if your job is physically demanding, such as construction), use 1.7. If you’re in between, use 1.5.
BMR x activity multiplier = TDEE
Keep in mind that TDEE is an estimate. Tracking your weight, measuring your waist, noting how your clothes fit and how you appear in the mirror will let you know how well things are going. Track your progress and adherence and make adjustments over time. Adjusting in small increments (100 calories) will help you hone in on the right numbers for you with greater precision.
Now that we know this, I have a very important question for you:
What is your goal?
Are you trying to lose fat? Build muscle?
If you’re trying to lose fat, you will need to be in a caloric deficit. That means you’ll need to eat fewer calories than you burn. Determining the size of the deficit will depend on you, how much weight you want to lose, the time frame, and your tolerance. Your deficit should never take you below your BMR. Eating below your BMR can lead to adverse health consequences. If you wanted to lose an average of a lb. per week, you would aim for a deficit of 500 calories per day. In this instance your daily calories would equal TDEE minus 500. (There are approximately 3500 calories/lb. divided by 7 days per week)
Generally speaking, the more overweight a person is, the greater the deficit he or she can tolerate. He or she may opt to drop fat faster than a rate of 1 lb./week. Remember, your deficit should never take you below your BMR.
Some good news about being in a deficit is that for the most part, meal frequency doesn’t matter. You can eat 2 meals a day or 12, as long as you’re hitting your calorie targets, you’re good.
Frame your deficit to be as enjoyable as you can. There is no need to starve yourself. The deficit should be just enough to keep the scale moving in the right direction at a moderate pace. If you prefer eating several times a day, do that. If 3 larger meals suits you better, do that.
Without going too far into macronutrient portions, a good guideline is to eat around .8-1g of protein per lb. of body weight. Protein will help you maintain muscle despite being in a calorie deficit. A 200 lb. person would aim for 160-200 g of protein per day. Protein yields 4 calories per gram, so that would be between 640 and 800 calories per day. This is just a guideline, so adjust as necessary to suit you.
The remainder of the daily calories should come from a combination of carbohydrates and fats that is most enjoyable and sustainable. Despite the bad press, both carbs and fats are healthy and important, so I don’t recommend going below .3 g per lb of lean mass.
You want this to be as painless as possible for adherence and sustainability.
To gain muscle, you will need to be in a caloric surplus. You’ll eat more calories than you burn. You will gain muscle as well as fat. We all wish there was a way to just gain muscle. You want to manage the surplus so that you minimize the fat gain.
Start at about 10-20% above your TDEE and adjust from there. That means TDEE x 1.1 or TDEE x 1.2. Muscle building is a fairly slow process. A person just beginning training can gain about 2 lbs. of muscle per month. Unfortunately those more advanced in their training will gain at a slower rate. If the scale goes up by 10 lbs in a month, please understand it’s not all muscle.
Again, you will want to make sure you eat enough protein. Protein is made up of amino acids which are the building blocks of muscle. Even though you’re in a surplus that doesn’t mean more protein equates to more muscle. Your target should be around .8-1g of protein per lb. of LBM per day.
A 150 lb. person would eat 120-150 g of protein daily (which correlates to 480-600 calories). The remainder of the calories should come from a healthy combination of carbs and fats. I recommend a higher percentage of carbs as it tends to help with resistance training.
Track your progress and adjust as you go along. I can’t say this enough. It really is the key to attaining your goals.
So there you have it.