Dieting’s effect on gut hormones!
Posted on April 2nd, 2018
I posted the image above on my instagram stories a few weeks ago and loads of you asked about it, so thought I’d share some snippets from some of the stuff I’ve been learning about the dangers of dieting in my Msc clinical nutrition course, and why loosing weight isn’t as simple as calories in and energy out!
The simple energy equation
But it’s not that simple…..
Image: The Scientific American
Before I continue I just want to say that I adopt a health at every size approach and therefore I would never be endorsing weight loss as a goal for health or happiness. I’m only talking about it here to illustrate the shortcomings of dieting and not because I want to promote some other weight loss solution. If you want more evidence on the health at every size approach please check out Linda Bacon’s book!
Despite the repeated evidence that diets do not result in meaningful long-term weight loss, lifestyle interventions such as calorie controlled dieting are still recommended as first-line obesity intervention. And that’s before you add in negative consequences of dieting on mental health! Moreover, evidence actually suggests dieting leads to overall weight gain due to physiological changes that occur in the body.
For simplicity, I’m going to focus on 3 important gut hormones that influence hunger and satiety impacted on by dieting – Ghrelin, Peptide YY and Glucagon-like peptide-1 (GLP-1). In reality, it’s A LOT more complex than this and there are many other biological factors including bile acids, nutrients, genes and the gut microbiome which can influence energy and glucose homeostasis.
Anyways back to Ghrelin, Peptide YY and GLP-1! Under normal circumstances peptide YY and GLP-1 increase when we eat a meal. In turn, they act upon the brain’s homeostatic reward pathways to reduce hunger and increase satiety, the response we ideally want from eating. Conversely, Ghrelin is the hormone that makes you feel hungry and signals you need to eat, once you’ve eaten ghrelin is inhibited so that feeling of hunger disappears and you feel satiated. Ghrelin is often vilified as this “bad” hormone that makes us feel hungry, but newsflash, you need to eat to stay alive and thus ghrelin is an incredibly important natural player in our innate hunger and fullness cues.
What happens during low-calorie dieting?
Well, these gut hormones change, and they change in a way that dysregulates our appetite and favours weight gain! Levels of Peptide YY and GLP-1 have been found to be reduced in dieters. This means they fail to signal to the brain that the body is full after eating. The effect is increased hunger and reduced satiety even with food intake. Further, hunger hormone ghrelin is increased, and again this isn’t suppressed properly after a meal so we continue to feel hungry even after food intake. This is why diets can so often result is miserable failed attempts – it’s not lack of willpower, it’s that you’re literally fighting your biology and primal drive to eat.
Like I mentioned these 3 hormones are a very simplified view of the overall picture. In reality, there are many more intricate physiological processes at play during calorie restriction including a slowing down of metabolism and reduced resting energy expenditure. These are the bodies way of protecting itself from what it thinks might be a famine! It’s conserving its energy stores and resisting weight loss because actually, it is far more smart than us and our diets.
SO the real question is, why is dieting still being endorsed to patients with obesity, to the general public, and particularly to those who are vulnerable to feeling inadequate in their bodies, like children – the target of the latest weight watchers campaign?? Whilst dieting may result in a modest short-term weight loss, the scientific community is pretty much in consensus about the failure of diets in the long term! Not only are they a miserable process detrimental to physical health, but they also have profound implications on mental health and can promote a range of disordered eating behaviors from binge eating to full-syndrome eating disorders. And all this for something that doesn’t even work and has the ability to change physiological processes to favour the very thing they’re trying to prevent!!
The answer is that dieting is big business and our repeated failures and insecurities are highly profitable. The children eligible for free weight watchers today will be the paying customers of tomorrow. Regardless of age, weight, or current feelings towards your body, dieting is dangerous and it should come with a warning sign!
Thankfully, based on growing evidence, The Health at Every Size movement is starting to gain momentum. I now pretty much exclusively follow HAES professionals online and social media who promote a weight-neutral approach to health and lifestyle. As we speed towards the summer months the #bikinibody chat is pretty much inevitable but please do yourself a failure and DO NOT be tempted to fall for the diet lie!! There are plenty of ways to improve mental and physical health independently of weight through self-compassionate and health-inducing behaviours.
If you have fallen victim to the diet bandwagon, and trust me I’ve been there, please don’t feel like a bad person or freak out! The most important thing is that you stop now and start treating your body with proper nourishment and respect. If you’re looking for some reads on this then Linda Bacon’s Health at Every Size and Evelyn Tribole and Elsye Resch’s Intuitive Eating is a great place to start. Or else I highly recommend Laura Thomas’ podcast Don’t Salt My Game. Freedom from dieting and demons it entails is liberating and beneficial for our mental and physical health, it’s about time we listened to the hard scientific facts over the powers of diet culture and image orientated society!