If we are speaking strictly about calories (ignoring all of the other factors that affect weight loss) it takes a deficit of 3500 calories in order to lose one pound of fat. What is a calorie deficit you ask? It’s when you take in fewer calories than is required for you to maintain your current body composition and energy function.
Kind of like when you overdraft your bank account (yikes) and you enter the red zone - that energy needs to be made up from somewhere and so it taps into your stored body fat to create energy. This is how fat loss works. If you are taking in less energy than you need to fuel your exercise and daily movement, then your body has this awe-some power to create that energy from those pesky love-handles you’re always complaining about.
Actually, when you stop to consider it, your body is pretty damned amazing.
Your body has a unique calorie requirement in order for it to perform all of your normal functions like breathing, keeping you upright and keeping your organs running smoothly. This is known as your basal metabolic rate (BMR) and will depend on things like your age, height, muscle mass, body fat composition and gender.
Just to be clear, your BMR is the minimum calorie requirement you need in order to function well and survive. This does not take into account your activity throughout the day like exercise or like walking up the stairs. Your BMR is a calorie level it’s not considered safe to go under. So if you are considering an insanely aggressive fat-loss protocol, eating fewer calories than your BMR can begin to cause adverse reactions (like chronically high cortisol).
So, eating in a deficit of 3500 calories will cause one pound of fat loss and it’s ideal to spread that out. Nutrition professionals recommend losing no more than 1% of your bodyweight per week. So if you weigh 200lbs, you’re looking at a safe weight loss of about 2lbs each week. And this is under the most ideal circumstances. Let’s look at the math of how that would break down into a calorie deficit:
Wow, that’s a pretty extreme drop in calories to take on overnight. If you’ve ever strictly tracked calories, you know how little food 1700 calories actually is (especially if you enjoy butter and avocados like me). A more modest approach could look like this:
A little easier to swallow (no pun intended) and one pound of fat loss per week is a great achievement especially if it’s done many weeks in a row. I often see new clients disappointed with only losing one pound in a week and this makes me deeply sad. Any weight loss is positive progress and my answer to them is this - “yes, but what if you can do this for 52 weeks straight? You’ll have lost 52lbs!”
That makes them stop and think about the dedication that will be involved in their weight loss transformation. Losing 50 pounds in a year and cultivating new healthy habits to keep that weight off would be incredible. Losing 50 pounds in four months and then gaining it all back because you crash dieted and then got derailed during the holidays is way less impressive. Which camp do you want to be in?
Here’s the thing though - in order for you to figure out your calorie deficit, you need to first determine your maintenance calorie requirements (unique to your body and level of activity), which is pretty much impossible without spending quite a long time tweaking that and figuring it out by trial and error.
This is why following a meal plan or nutrition program that gives you a calorie assignment without knowing anything about you is almost always going to be bullshit. It’s just a complete guess or a generic formula that is based on a few, simple metrics like weight and age and doesn’t accurately reflect you as an individual. When it comes to calorie requirements we are all unique snowflakes. Calories aren’t everything. It’s often more ideal to learn strategies to lose weight without relying on calories.
Hopefully this all has shed light on why diets that promise 20 pounds of weight loss is XX amount of time are always a scam or a marketing ploy. You losing 20 pounds will look very different from your neighbor or cousin losing 20 pounds. A safe process for losing weight is to adhere to the rule of 1% of your bodyweight per week (or perhaps half that speed) using methods that allow you to build new, healthy habits and integrate them over years.