How To Determine The Number Of Calories You Should Eat To Lose Weight

How to Determine the Number of Calories You Should Eat to Lose Weight

When you start a diet, determining how much to eat can feel a bit like playing calorie roulette. Many people turn to a calorie calculator, but they can greatly overestimate the amount of food that you need to lose weight. Here's how to calculate your own target.

Images by openclips, epsos, Michell Joyce, 16:9clue

Note: yes, we know that kilojoules are the metric unit, and widely used in Australia. However, many dieters also use calories for measurement, and the principles are the same whichever system you adopt.

Step One: Find Your "Caloric Maintenance"

How to Determine the Number of Calories You Should Eat to Lose Weight

Weight loss revolves around the concept of calories. Simply put, a calorie is a unit of energy. You expend calories as you go about your daily life doing everything from exercising to simply breathing and staying alive. You consume calories when you eat or drink calorie-containing foods.

From a broad perspective, the basics of weight loss and weight gain are straightforward: when you eat more calories than you use (in which case you're in a "caloric surplus") you gain weight. Conversely, when you use more calories than you eat (in which case you're in a "caloric deficit") you lose weight.

So, in order to stay the same weight, you want to find your "caloric maintenance": The area where the calories you consume equal the calories you use.

There are two ways that you can determine your caloric maintenance. The first is a calorie calculator. However, if you've used calorie calculators before, you may have noticed that they can grossly overestimate the amount of calories that you need to eat daily in order to lose weight. This is partially because they don't take into account the amount of muscle -- or lean body mass -- that you currently have.

An individual with more lean body mass will have a higher caloric maintenance than someone with less lean body mass, all other things being equal. I recommend the exrx calculator, which is more accurate than most calculators since it includes "lean body mass". So, for best results, be sure to input your approximate body fat percentage. If you don't know yours, you can figure it out by using Leigh Peele's guide here.

Alternatively, you can also use these handy lookup tables that I modelled from client data. While this lookup table is surprisingly accurate for only requiring one measurement, it should only be used as a rule of thumb.

Men: Waist (cm) BF% Women: Waist (cm) BF%
63.5 5% 63.5 15%
66 6% 66 15%
68.6 7% 68.6 16%
71.1 8% 71.1 17%
73.7 9% 73.7 18%
76.2 10% 76.2 21%
78.7 11% 78.7 23%
81.3 13% 81.3 26%
83.8 15% 83.8 28%
86.4 17% 86.4 31%
88.9 19% 88.9 34%
91.4 21% 91.4 37%
94 23% 94 40%
96.5 26% 96.5 43%
99.1 29% 99.1 46%
101.6 31% 101.6 48%
104.1 34% 104.1 51%
106.7 36% 106.7 53%
109.2 39% 109.2 56%
111.8 42% 111.8 58%
114.3 44% 114.3 60%
116.8 46% 116.8 62%
119.4 48% 119.4 63%
121.9 50% 121.9 65%
124.5 52% 124.5 66%
127 54% 127 67%

The second method is to log what you eat over the course of a few days using your favourite nutritional tracker. The caveat here is that the very act of writing down what you eat will change your actions, but do your best to eat normally. If you've been losing or gaining weight recently, then your calorie log might not be the best method of predicting your caloric "maintenance", since you might have been in a caloric surplus or deficit.

In fact, you can use both methods to make a reasonable guess -- just average the two numbers together. If you feel that you've done a poor job mimicking your diet over the past few days of logging, err closer towards the calculator. On the other hand, if you feel like you've done an excellent job and the calculator is off, err towards your logged averages.

Step Two: Set Your Protein and Caloric Targets

How to Determine the Number of Calories You Should Eat to Lose Weight

Now comes the easy part. Once you figure out your caloric maintenance, it's time to calculate two things: the amount of protein and the number of calories that you'll be eating. Protein is important, because it will allow you to keep your lean body mass (and thus your metabolism) high in a caloric deficit. It's also the macronutrient that will keep you the most satiated while you're dieting.

Take your maintenance calories from the previous step and subtract 20% from it. That will be the number of calories you'll be targeting each day. For example, if your maintenance is 2000 calories, you'll be aiming to eat about 1600 calories. You don't have to hit 1600 on the dot every day; a margin of error of 5% or so is fine (so, in this example, that's anywhere between 1520 to 1680 calories per day).

Next, we'll use nutritionist Alan Aragon's method to figure out your protein target. Decide your goal weight (in pounds) and strive to eat that amount in grams of protein. For example, if you currently weigh 200 pounds and want to eventually weigh 130, consume 130 grams of protein daily. If you're not used to eating protein, then you might not be able to hit this amount at first. Do your best, and hit it as closely as possible. If you don't mind supplements, adding whey or casein protein may help you reach this number.

By the end of this process, you'll have all of your necessary targets to begin your diet. This doesn't mean automatic success, obviously. It will be important to be both mindful and flexible during your diet, as well as develop all of the necessary skills for success. Having a solid set of calorie and protein targets, however, will do wonders for starting you off on the right foot.


    Can I suggest you also go watch That Sugar Film. Not all Calories are equal.

    US Navy Body Fat Calculator is your friend. More accurate than your table up there.

    Pretty sure they are equal from an energy stand point of view, not accounting for the small thermogenic effect food has, a calorie is a unit of measure, that's like saying not all centimeters are equal...

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