How Much Do You Actually Need To Eat To Lose Weight? Maintenance Calories Explained.
If well-meaning colleagues, friends or family members and search results on Google are to be trusted, the magical number of calories for a successful diet is 1200 calories. While 1200 calories might lead to rapid weight loss in the beginning simply due to the very low calories intake which causes significant calories deficit (read: this article to find out why a calorie deficit is absolutely necessary for weight loss), it’s neither sustainable nor nutritionally sound in the long run. How much nutritionally-dense foods can you fit within a 1200 calories window?
There is no “one-size fits all” number of calories that people need each day to promote weight loss.
Since energy balance determines the extent of weight loss, the amount of food (or the number of calories) you need each day really depends on the the amount of energy you expend every day.
What Maintenance Calories Are
What are maintenance calories? Well, exactly what they sound like — they’re simply the number of calories you need to consume within a day to maintain your weight. Given that the maintenance of weight relies on the following equation:
Calories In = Calories Out;
We can roughly approximate the “Calories In” portion of the equation by calculating the “Calories Out” portion. “Calories Out” is also known as “TDEE”, or “Total Daily Energy Expenditure” and consists of 4 basic components. For a more detailed breakdown on the various meanings of the components, read this article.
Calories Out (TDEE) = BMR + NEAT + Exercise + TEF
Calculating Basal Metabolic Rate (BMR)
Since your BMR contributes to roughly 60% of “Calories Out”, this is naturally the starting point of our calculations. BMR is largely dependent on 2 factors: Fat Mass (FM), and Lean Body Mass (LBM).
Fat Mass (FM) = Body Weight*Body Fat Percentage
Lean Body Mass (LBM) = Body Weight — Fat Mass
LBM is more metabolically active than FM, and contributes to TDEE to a greater extent, which is why it is of paramount importance to separate LBM from FM. An important point to take note is also that LBM is not simply your muscle mass — other than muscle mass, it also includes the weight of your hair, organs, bones, fluids contained in the stomach at any given point of time, etcetera. As long as it’s not fat in your body, it is classified as LBM.
Once you have settled on an appropriate way of measuring your body fat which makes the most amount of sense to you (regardless of whether it’s through skin callipers, BIA, DXA scans, Bod Pod…), ensure that you are consistent in the method of measurement, and that you’re always measuring in the exact same way, every time. For example, let’s say my weighing scale gives me a measurement of my body fat percentage — I must always weigh at a specific time every single day (immediately upon waking up, for example) for the numbers on the scale to be significant. Since LBM consists of all matter within your body which is not fat, even drinking a glass of water can change the readings on the scale within a few minutes!
Alright, once you’ve gotten the numbers of your body weight and body fat, we can finally get to calculating your BMR. While there are many equations out there, I’ll simply go through the Müller equation as it accounts for most of the variables which have the biggest impact on metabolic rate — LBM, FM, Sex and Age.
BMR = (13.587*LBM) + (9.613*FM) + (198*Sex) — (3.351*Age) +674
Getting to TDEE (Calories Out)
Your estimated TDEE will depend on your activity factor, and that depends on how active you are on a daily basis. The following is a rough guide to the factor you need to multiply your BMR with to arrive at the best estimate of your maintenance calories at this point.
Sedentary — Multiply by 1.2
- Desk job
- The word “exercise” doesn’t exist in your vocabulary
Light Activity — Multiply by 1.375
- Desk job
- You get to the gym… sometimes.
- Or you don’t exercise, but are on your feet most of the day at work
Moderate Activity — Multiply by 1.55
- Desk job but you go to the gym ~5 times a week; or
- You get to the gym sometimes and are on your feet most of the day at work
Very Active — Multiply by 1.725
- You train like a mad person most days of the week, and you are also on your feet most of the day at work
Extra Active — Multiply by 1.9
- You train like a mad person, and you work a physically active job
Let’s say you came to the number of 1600 for your BMR, and you’re a Very Active person, your estimated TDEE would then be 1600*1.725 = 2760 calories.
Now, bear in mind that this is not a holy grail number; it is simply an estimate — your body will almost always certainly behave differently from the prediction of a Mathematical equation (even though it can be quite close).
Fine-tuning the number
The best way moving forward is to consume 2,760 calories and monitor to see if you are indeed maintaining your weight. If you lose weight, you need to increase the number of calories you are eating to get to your maintenance calories. If you gain weight, you need to cut down on the number of calories you are eating to get to your maintenance calories. How many calories to cut, or how many calories to gain?
Bear in mind that 30% of LBM is protein (70% is water), and 87% of FM is fat (13% is fat) — if you unfortunately put on 2.5KG after 28 days (0.625KG of LM, and 1.875KG of FM), we can calculate the excess calories consumed over the period of time.
Excess calories from gain in LM = 625 grams of LM * 30 percent * 4 calories per gram of protein = 750 calories
Excess calories from gain in FM = 1,875 grams of FM * 87 percent * 9 calories per gram of fat = 14, 681 calories
Total excess calories in 28 days = 15,431 calories
Excess calories in 1 day = 551 calories
A more accurate TDEE for you would then be 2,760 calories — 551 calories = 2,209 calories.
Calculating number of calories for weight loss
Ah yes, finally, after all that Math — we are just one step away from the individualised number of calories you need to eat in order to lose weight. Are you excited? In general, for a more sustainable weight loss in the long term, an average of 0.4 to 0.8 percent of body weight loss per week is encouraged.
Let’s say you’re at 100KG now, and you’d like to lose 0.6% of body weight per week — that’s 600 grams per week.When you lose weight, you have to realise that not all of it comes from fat mass: you’re also losing some of your lean body mass. While the exact ratio of fat mass to lean body mass loss varies from person to person and from circumstance to circumstance, 80:20 (480 grams of fat mass, 120 grams of lean body mass) serves well enough for a rough guide. Getting into the exact percentages will require another article all together. (Let me know if you’re interested, though!) 😉
Calories from FM lost = 480 grams * 87 percent * 9 calories per gram of fat = 3,762 calories
Calories from LBM lost = 120 grams * 30 percent * 4 calories per gram of protein = 144 calories
Total amount of calorie deficit required over a week = 3,762 calories + 144 calories = 3,906 calories.
Daily calorie deficit required = 3,906/7 = (rounded) 558 calories
Simply subtract this amount from the TDEE you obtained, and voila, your very own number of calories you need to consume to lose weight.
Hopefully, this article was useful for you, and that you no longer have to force yourself on a measly 1,200 calories diet in a desperate attempt to lose weight for the nth time.
PS: In case anyone thinks that calorie-intake should be everything you think about, I’m just here to say that it shouldn’t. When losing weight, in addition to caring about your calorie balance, you should also be concerned with the quality of your diet (i.e. micronutrients).
Thanks for reading! If you want an evidence-based approach to your nutrition, start by learning how much protein you need for your fitness goals. You’ll like it — I promise!