The 3,500 Calorie weight-loss rule is bullshit
Professionals in the medical and nutrition fields know the 3,500 Calorie weight-loss rule is garbage. The fact that so many still use it dooms people to weight-loss failure.
Advocates of the 3,500 Calorie rule claim that for every 3,500 Calories you cut from your diet, you will lose a pound in weight. And for every 3,500 Calories you add to your diet, you will gain a pound in weight.
This is bullshit. Complete and utter bullshit.
Thanks to metabolic adaption, that smaller slice of cake doesn't lead to permanent weight loss, and a larger slice doesn't lead to permanent weight gain either.
What's more, we have known that the 3,500 Calorie rule is wrong for at least 50 years.
In 1962, scientists at Guy’s Hospital, London, published a study that clearly demonstrated that the 3,500 Calorie rule doesn’t work for weight gain. Five medical students were asked to eat normally and record what they ate every day for a five-week period. They also had a tube inserted directly into their stomachs through which they were fed a liquid supplement every night before going to bed. The supplement looked the same on every night, but its Calorie content varied: some nights it contained no Calories, some nights 2,000 Calories. The students were weighed daily, but not told what they weighed.
The first thing of note was that no matter the Calorie content of the supplement, the students continued to eat the same number of Calories as they did in a no-supplement control period. Participants were therefore consuming more Calories than they would normally do when given the 2,000 Calorie supplement.
The second thing was how little weight the students gained in comparison to expectations. One student, for example, was given the 2,000 Calorie supplement for 36 nights. This meant consuming an additional 72,000 Calories. That should have resulted in a 20lb (9kg) weight gain according to the 3,500 Calorie rule. The student did gain weight, but barely 4lb (2kg). Another student gained nearly eight pounds (3.5 kg) instead of an expected 15lb (7kg).
The study’s authors found their findings scarcely believable, calling them “remarkable”. They couldn’t explain what had happened to the additional energy, but it’s now clear that your body acts via metabolic adaption to prevent both weight gain and weight loss.
In 1970, obesity expert, George Bray, wrote an article entitled, The Myth of Diet in the Management of Obesity. In it he states that adaptive changes that occur during dieting require “considerably greater Calorie restriction to produce a meaningful weight loss” than convention dictates. Bray then calls out the 3,500 Calorie rule specifically, saying that a daily reduction of 1,000 Calories results in a weight loss of just 0.8lb in a week, not the promised 2lb.
The 3,500 Calorie Rule - you do the maths
Now, you might be thinking does it really matter if the 3,500 Calorie rule isn't bang on the money?
Surely weight loss still comes down to counting Calories in and out?
And if that's the case, what harm a general rule of thumb for how much weight you will lose by cutting out Calories?
Well, let’s look at the numbers.
According to the 3,500 Calorie rule, to lose 2.2lb or 1kg of weight requires a reduction of 7,350 Calories. That’s what should happen if weight loss comes down to counting Calories in and out.
Now let’s see how metabolic adaption feeds into the equation. Fortunately, the National Institutes of Health (NIH) has done the maths for us. Accounting for metabolic adaption, the NIH predicts that each 24 Calorie change in daily energy intake will eventually lead to a 1kg change in weight. The key word here is eventually. Half of that weight change will occur within a year and 95% of that weight change will occur within three years.
This means that to lose 1kg in weight requires a diet containing 26,000 fewer Calories over three years, not 7,350 fewer Calories over one year.
That’s more than three times what the 3,500 Calorie rule says.
To lose one pound of weight permanently requires something closer to a 10,000 Calorie reduction. When you consider a man is said to require 2,500 Calories a day, losing a pound in weight mean eating 500 fewer Calories a day for a week, it means eating nothing at all for four days!
No wonder there are so many disappointed dieters out there.
Take a man weighing 100kg (15st 10lb or 220lb). According to the 3,500 Calorie rule, eating 500 fewer Calories per day than required for his energy needs would lead to a 52lb (23.6kg) weight loss after a year. Accounting for metabolic adaption, the NIH predicts that a 100kg man with a daily Calorie deficit of 500 Calories would only lose about 21lb (9.5kg) in a year. One year according to the 3,500 Calorie rule to lose 52lb, three or more years in reality.
You can’t get more mainstream than the NIH because it’s part of the U.S. Department of Health and Human Services. And it’s not as if the NIH figures are based on cutting-edge research either. As detailed above, we've known the 3,500 Calorie rule is bullshit for decades.
And here's the problem. When someone on a diet isn't losing weight as quickly as promised, he or she will feel like a failure. And people who feel like failures give up.
So, to every health organisation and every health professional in the world still lazily touting the 3,500 Calorie weight-loss rule to the overweight, I say this. We deserve better, so much better, than tired out-of-date misinformation.
You know people won't lose the weight claimed when following the 3,500 Calorie rule. You are setting up people to fail, sending them over the top armed with information that will see them flounder in no man's land.
At Belly, we will always strive to give you the best intel so that you can successfully wage war on fat. Hence our motto: Led by science. Not donkeys.
And when you follow the science, it isn't just the 3,500 Calorie rule that doesn't stand up. Counting Calories full stop is a fool's errand.
REFERENCES
- Effect of Nightly Food Supplements on Food Intake in Man (The Lancet)
- The Myth of Diet in the Management of Obesity (The American Journal of Clinical Nutrition)
- Quantification of the effect of energy imbalance on bodyweight (The Lancet)
Article last updated: 30th January 2021
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