Diets Don't Fix Obesity, They Cause It - Time To Undiet!

posted on: March 08, 2026. posted in: Weight loss, Dieting

"Hey Liam, what do you do for a living?"

"I try to convince obese people not to diet."

"What? Why would you do that? They need to diet!"

"Hmm, you'd think so. But actually it's their dieting that has made them obese in the first place."

"That's nonsense! How can dieting make someone fatter! Surely if you're in a calorie deficit you lose weight!"

"Nobody's debating that. If you're in a calorie deficit, eating less than you burn, of course you lose weight. But the issue is what happens when they inevitably come out of that calorie deficit."

"What do you mean?"

"Well Jenny is 13. She signs up to Weight Watchers. She goes on their diet and goes into calorie deficit. She loses weight. Great! But eventually she gets to the point she cannot sustain the calorie deficit. Her body and brain fights back. Her metabolism slows. Her appetite increases. She loses control and binges, then regains the weight."

"Yeah, I've heard that happens. But surely she just needs to get back on the diet then she'll lose it again. Simple."

"Not so simple, unfortunately. You see, we now have the science to prove that every diet you do causes a small adaptation to your metabolism and appetite. In short? Your metabolism gets a little bit slower. Your appetite gets a little bit bigger. And this is your body and brain fight back against the diet."

"Right. So the next time she tries Weight Watchers at age 14 she's trying it with a slightly slower metabolism, and slightly higher appetite, making the diet and the calorie deficit harder to sustain?"

"Exactly. So yes, she loses weight again. But not as much, and she binges even more and regains even more when she falls off Weight Watchers for the second time. Except it's not really her 'falling off' the diet, it's her body and brain adapting to the diet."

"Wow! That's mind blowing! So now she tries another diet, and I'm guessing her metabolism is even slower and her appetite is even bigger. So if she joins Slimming World she's still going to lose weight, but the cycle repeats itself."

"You've got it. And I've been training people for 20 years, watching them go through that process. It's practically a carbon copy from client of mine to client of mine. Starting diets with a normal metabolism and appetite at about age 13, then by the time they reach their 40s and 50s they have the metabolism of a slug and the appetite of a shark, producing huge amounts of weight gain."

"Wow. So they do a few rounds of Weight Watchers and end up even fatter. Then they do a few rounds of Slimming World and end up even fatter. Then they do a few rounds of meal replacements, then end up even fatter."

"Exactly."

"Blimey, these diet companies are awful! Why don't they warn their customers about this??"

"Well, it's not really in their interests. The have the perfect business model. They sell people diets that produce weight loss in the short term, but that gradually slow your metabolism and increase your appetite in the long term. So you always regain the weight, which means you always come back."

"Madness! It's like a dodgy bike company selling you a bike with tyres that they know will go flat, so you keep coming back to them to buy a whole new bike every couple of years! Why aren't there other people out there warning obese people and telling them not to diet?! Surely there are scientists who know this??"

"There are loads. They are just a lot more polite than me and don't rant as much, so they don't get noticed as much."

"Like who??"

"Well Professor Traci Mann wrote a book called Secrets From The Eating Lab that explains all the science behind this. Professor Sandra Aamodt wrote a book called Why Diets Make Us Fat, that explains how chronic dieting produces weight gain. The science and research in these books will be common knowledge one day, but for now the public are largely unaware of the risks of dieting."

"So what should obese people do if they can't diet?"

"Well, they have to undiet."

"Undiet? What's that?"

"My next post!"

Liam x