How Much Weight Can You Lose in a Week

The question for this week is a very common question asked by people attempting to start their quest for weight lose. How much weight can you lose in a week?
For starters lets break down the intention of the question, this question is usually asked as to help the exercise decide what is a fair weight loss goal to set for themselves. So what is a fair goal to set for weight loss in one week (7 days) ?

Huge initial weight loss

We’ve all seen the first week of the biggest loser. Whereby the contestants drop ungodly amounts in their first week. For instance Rulon Gardner losing a hulking 14 kilos in just 7 days!

14 Kilos of Fat is 98000 Calories. This show could have you believing that Rulon Gardner ran at a calorie deficit of 14000 calories a day. As on the show they are on a hugely restrictive diet lets allow 1500 Calories a day for food intake, this would appear that his body has burnt 15500 calories in just one day!

So how can we explain this weight loss?

Basal Metabolic Rate – the number of calories per day that your body burns in order to sustain itself (think heart beating, lungs breathing). For a 6’2, 40 year old, 215kg, man this approximates to 4600 calories a day! If Rulon were to sit on his butt all day he still burns 4600 calories!
But there is one major component of weight loss we are missing, how much of the 14kilos was actually fat loss and how much was water weight?

This can be explained by a study from the 70s that showed when on a highly restrictive carbohydrate diets (such as Atkins diet, low calorie diets, starvation diets) that 60% of the weight loss can be due to water weight. When the body is restricted of carbohydrates it uses up its supply of glycogen, think of glycogen as a matrix of water and sugars. When the body has no carbs from your food intake it will call on these glycogen stores for energy, and once the carbs from the glycogen are used the water is then released.

With this in mind it appears that he has not burnt 15500 calories a day, but merely 40% of this number, which would take us to 6200 calories a day. But we also need to subtract the 4600 calories required by the body to simply run the body of this gigantic man. We are left with around 1500 calories!
How could he burn 1500 calories? Quite easily, for a man of his size, a simple walk for 60 minutes will burn a whooping 900 calories! (I’m using the term “simple” quiet loosely here, doing anything while 215kg would be extremely taxing, but he is an ex-Olympic gold medalist, so I’m guessing his made of stronger will then 0.00001% of the population.)

A weight loss goal over 7 days

You will find the body operates closer to a two week cycle then a one week cycle and it often takes 3 cycles for visually noticeable weight loss. So a more realistic timeframe is 6 weeks. Let’s reframe the question.

How much weight can you lose in 6 weeks?

The short answer is 6kgs. As a generic general rule this is a safe bet.  As nearly everyone has the ability to lose this amount of weight. 6kgs of fat equates to a calorie deficit of 1000 calories a day.
If you 215kgs like Rulon and burn 4600 calories a day existing, this means only ingesting 3600 calories a day.
Say if your Sally a 20 year old, 5’6″, 60kg, female, this would mean eating 1500 calories a day and exercising for 500 calories a day. (-2000cals Basal Metabolic Rate + 1500 Food -500cals exercise = -1000) .
As you can see from above the task becomes more difficult the lower your weight.
 
How do you lose 6kgs in 6 weeks?

Let’s make this as simple as possible,We want our daily calories to be in a deficit of 1000 calories.

BMR + Food Intake + Exercise = -1000.
In our example above Sally’s BMR = -2000, and we want to be at -1000 calories for the day.
She could do no exercise and only eat 1000cals
-2000 + 1000 + 0 = -1000
She could eat 1500cals and do 500cals exercise
-2000 + 1500 – 500 =  -1000
She could eat 2000cals and do 1000cals exercise
-2000 +2000 -1000 = -1000
She could eat 2500cals and do 1500cals exercise
-2000 +2500 -1000 = -1000

This highlights how difficult it becomes to lose weight as your Food Intake calories increase. Eating 1500 calories and doing 500 calories of exercise is an easier task then eating 2500 calories and exercising off 1500 calories.  Once the calories get high it becomes almost impossible to exercise off the excess.