Crash diets and why ultimately, they don’t work.

Before I start this next blog, I want to state that a lot of the information I have learned about this topic has come from Dr. Layne Norton (pics below). I have been a follower of this man for over ten years. He is a refreshing and leading figure in the world of nutrition, bodybuilding and powerlifting and is well worth a follow on all his social media and website platforms, he has also just released a book which I would highly recommend, you can find him at














I have decided to write about this topic as by far and away, as a personal trainer or coach one of the most popular, if not THE most popular question you’ll be asked about is “what’s the best way to lose weight?”. The simple answer is of course “you need to be in a calorie deficit”. This means you need to be burning more energy than you are consuming. Simples! No need for magic teas, detox, Keto, Paleo, Operation Transformation (don’t get me started), Atkins, gluten-free diets, popup celebrity diets etc etc etc. As I’m sure you are aware there are many many diets pertaining to be the best for weight loss and, for most, they will all achieve it.   Calories in versus calories out. Whatever “diet” helps you best achieve that is the best one for you. Many “diets” work. I put “diet” in inverted commas as when people tell you about their new “diet” (often at social gatherings and places I’ve no interest in talking about it) they refer to a short-term lifestyle choice. Most of the time talking to these people they have tried multiple diets, stopped them, regained the weight (often worse). This isn’t surprising considering less than 20% of individuals that have tried to lose weight are able to achieve and maintain that weight loss over a year. Weight loss is never an issue, weight loss maintenance is!

Your metabolism is defined on google as “the chemical processes that occur within a living organism in order to maintain life”. “Maintain life” is crucial in this sentence as, contrary to popular belief, the body has little to no interest in “bulking”, “cutting”, having a six-pack, doing a triathlon, running a marathon, playing championship etc etc. It’s first priority is survival and so long as it’s getting the necessary nutrients to support its survival than it is happy with that. What happens for a lot of people is they take in more calories than their body/lifestyle requires and so body fat is accumulated. Often this fat is accumulated over months or years and they then want to lose it in a matter of weeks. The following is an explanation as to why this is not a sustainable nor ideal long-term goal.

In a paper titled “Biology’s response to dieting: the impetus for weight regain” by Paul S Maclean et al they propose that the body starts off with what is termed a body fat set point, that is to say that your fat cells (fat storage) has already been predetermined based on a number of factors including diet and training history, body type, stress etc. In it the paper proposes that weight loss in individuals occurs through a decrease in fat cells size and not actually fat cell quantity. When you reduce your calorie intake these fat cells shrink. While trying not to get too technical the hormone imbalance (from leptin and ghrelin) that occurs through these fat cells shrinking causes hunger levels to rise, ie when people go on a crash diet (decrease their normal calorie intake to drastic levels below what they normally take in) they find themselves constantly hungry despite often the diet requiring them to eat more regularly. While we’re slightly on topic you cannot increase your metabolic rate by eating more regularly and you don’t “kickstart” your metabolism in the morning by eating breakfast. Below is a simple illustrative example of what occurs when an individual both decreases their calorie intake drastically and then invariably goes back to their usual eating habits due to the diet/lifestyle being completely unsustainable, unenjoyable or unrealistic. In it, it shows how the fat cells shrink once a drastic diet has begun, then once finished the diet, how the weight comes back on when their normal diet is resumed.


Due to the rapid decrease in calories and then subsequent refeed of these calories the body begins creating extra fat cells to accommodate for this extra energy in nutrient intake. From here the individual returns to their previous bodyweight and body fat % but with more fat cells than they started with. Then once normal cell size resumes the individual has overshot their previous bodyweight and bodyfat % and at this stage often begins another “diet” repeating the whole process again.

This is a common practice for many individuals who struggle to lose weight and also in competitive fighters for making weight. The more drastic the process is to cut weight for a fight the harder it is for the fighter to continue repeating this in order to get to the required fight weight. Some of the methods fighters typically use to cut weight drastically hinders performance and all their training camp results go out the window as a consequence.

The advice going forward is simple, stick with what’s sustainable. If you want to lose body fat, decrease your daily energy intake at a slow and manageable level. Don’t cut 1500 calories out of a diet that normally consists of 3000. Don’t reinvent the wheel. A diet that claims to drop 10 Kg in two weeks may be the one you need but not the one you want (yessir I made a Batman reference!). Lastly don’t think of a diet as something you want to do for a short time think of it as something you’ll do for life.



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