WE’VE ALL BEEN THERE – you have an event you told yourself you were going to get in shape for months ago. Time has come and gone, and you haven’t exactly given it your best effort. Before you know it, you have one week left to make something happen. Exactly how much weight can you lose in a week?
Click on any weight loss transformation story and you’ll see amazing feats of people losing stacks of weight in a matter of months. Sometimes that’s done healthily, and sometimes people take drastic measures to shed those kilos. Surely there’s a way for you to lose just 5 kilos in a week, right?
The answer depends on a number of factors. And, just because you can, doesn’t mean you should. We talked to experts to figure out just how much weight you can lose in a week, safely.
How much weight can you lose in a week?
The answer depends largely on the size you already are. The more weight you have on your frame, the more you’ll loose in a short amount of time. That’s especially true when you first start trying to lose weight, says David Creel, Ph.D., R.D., a psychologist and registered dietitian in the Bariatric and Metabolic Institute at Cleveland Clinic.
Some of this is simple math, but the bigger factor at play is that your body is fiercely protective over the weight you already have – so the longer you stay on a weight-reduction plan, the harder it can be to see the number move on the scale.
Here’s why: as we shed the kilos, our metabolism – i.e., our body’s internal fat-burning furnace – also starts to slow down, causing us to burn fewer calories than we used to. “It’s kind of like taking a backpack off,” says Dr Creel. “Breathing requires less calories, walking down the street requires less calories, everything requires less energy.”
The less you weigh, the harder your body will cling to the weight you do have, making it even harder for you to lose.
“Unfortunately, our brain doesn’t have a scale saying, ‘when you get to a healthy weight, we’ll stop all this compensation,’” he says. “It doesn’t work that way.”
So even though everyone wants to know the amount of weight they can lose in a week – and everyone wants that to be a big number – the answer isn’t always straightforward.
Like we said prior, there’s a difference between how much weight you can lose in a week versus how much weight you should lose in a week – and trying to figure out the former can be dangerous.
Here’s the thing about extreme diets, though – as much as you might want to lose kilos in the short-term, you’re not doing yourself any favours over the long-term. Very low-calorie diets can cause you to become dehydrated, so any weight you’re losing is probably primarily water weight, says Dr Creel (and let’s face it, that doesn’t exactly count).
Plus, extreme diets can also cause you to lose muscle, which can further hinder your metabolism. That’s because our muscles play an important role in helping our bodies burn calories throughout the day – the more muscle mass we have, the higher our metabolic rate.
“If someone goes on a pretty restrictive diet, they might lose 20 per cent to 25 per cent of their weight as muscle,” says Dr Creel.
Extreme examples aside, Konstantinos Spaniolas, M.D., associate director of Bariatric and Metabolic Weight Loss Center at Stony Brook University, says that losing one percent of your body weight per week is considered rapid, but within reason.
Say you start at 130 kilos – a goal of one per cent fat loss per week means you’ll shed three 1 and a half kilos a week. That can be reasonable. But if you’re just looking to drop a couple kilos a week from a relatively lean 70 kilo frame, you’ll probably have a harder time losing it – or at least, without losing some muscle mass.
How much weight is safe to lose in a week?
The general rule of thumb is about half to 1 kg per week, says Dr Creel. Even then, those numbers aren’t always consistent from week to week – it can be more of an average.
One Columbia University study showed just how much it matters for preserving muscle mass. For this research, scientists had people cut calories and then either do strength training or cardio workouts three times a week. After eight weeks, everyone lost more than 9 per cent of their body weight. But in the aerobic group, 20 per cent of that came from lean tissue (mostly muscle), while the resistance group limited lean-tissue loss to 8 per cent, while still trimming down overall.
To preserve muscle, you’ll also want to make sure you’re eating enough protein, which provides essential amino acids that your body uses to make muscle. Dr Spaniolas recommends eating about .8 to 1 gram of protein for every pound (450g) you weigh in order to retain muscle. There are plenty of ways to get that protein, including from these hearty vegan meals with more protein than a burger.
What factors affect weight loss?
Besides your starting weight, there are other factors that can make it easier or harder for you to lose weight. One of these factors is your dieting history. Not only will you burn fewer calories if you’re smaller, says Yoni Freedhoff, M.D., author of Why Diets Fail and How to Make Yours Work, but complex hormonal and metabolic shifts are also at work, making it harder to burn fat the longer you’re losing.
Scientists are still working to understand the mechanisms, but research has shown that people who have lost weight burn fewer calories than people who never dieted. That doesn’t mean you’re doomed. It just means you tend to lose weight faster at first.
Not getting enough shut-eye also throws hunger and metabolism hormones like leptin and ghrelin out of whack. In a small study published in Annals of Internal Medicine, volunteers on a reduced-calorie diet slept either 5.5 or 8.5 hours a night. In two weeks, they both lost a little more than 2.9 kilos – but those who slept more lost twice as much of that from fat. Sleep is so critical to everything that Men’s Health even put together the best sleep strategies and products to help you do it better.
Of course, your diet will also play a major role in how much weight you lose. Dr Spaniolas says correctly estimating how many calories your body needs is complicated, but recommends using a chart or calculator from the National Institute of Health. From there, you can omit about 500 calories per day to lose weight, but shouldn’t go much lower to begin with. And even then, he says it may not be easy to sustain this reduction in calories if you’re already lean and need fewer calories to begin with.
Watch what you drink, too: alcohol can easily increase your daily calorie intake if you don’t monitor those calories. Men consume an extra 433 calories on days they consume alcohol when they have a “moderate” amount of drinks, according to one study. You need to factor in calories from alcohol in any weight loss plan.
If you’re looking to lose a lot of weight or make bigger changes to your body, you might want to buy a body composition scale, which can measure fat, muscle mass, and more. (A tape measure and a mirror can also work.)
Just remember – it’s not all about the numbers. Sure, you might want to drop as much weight as possible one week, but a better question is, but what kind of changes to my lifestyle can I make that will improve my health over the long-term, says Dr Creel.
“There are other things to focus other than one-week weight loss,” he says.
This story originally appeared on Men’s Health U.S.
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