Why maintaining weight loss is so hard
Lessons from Life and the Literature
If you don't know anything about the physiology of appetite, or metabolic responses to weight gain and weight loss, the solution to the obesity epidemic seems very, very simple. If you accept that consuming more calories than you burn causes weight gain, then it seems reasonable to suggest that the way to lose weight is for people to consume fewer calories and try to burn more.
Recently a member of the House of Lords in the UK made some comments about the obesity pandemic and suggested that what the government should be doing is telling people that it is not acceptable to be obese and that they should eat less*
Lots of people got angry with this Lord, and said that he was stigmatising people and being hateful. His comments certainly were not helpful, or remotely constructive, and it's also pretty worrying that people are in positions of power and can contribute to national policy without knowing even the first thing about the subject they're talking about**.
However, I think sometimes for those of us who work in the area of obesity science or obesity medicine, it's easy to forget that the vast majority of people have never heard of ghrelin, or GLP-1. They don't know Kevin Hall’s research (and why would they?). ***
And I think the key here is - rather than yelling at people across social media - to educate people on the science of appetite hormones, or the effect of weight loss on metabolism.
And to be fair, I used to be a bit of an idiot myself.
For example, in 2007 I did one of my clinical rotations at the wonderful Methodist Hospital in Houston, Texas. The department I worked in had an amazing weight management program, which was very similar to the very low calorie diet interventions that we see now. Prior to working there in 2007, my thoughts in general were that obesity management was a lot of education on the calorie content of foods, and not consuming too much sugar and other things. (Yes, I really did think (I was an idiot in my 20s) that most people with obesity didn't know much about what they were eating. I'm also ashamed to say I thought willpower was also an important ingredient in successful weight loss).
I remember sitting in on one of the meetings they had with the participants of this program.
And every participant there (it was a really swish hospital so I think you needed quite a bit of money/amazing health insurance to get treatment there) was super successful - lawyers, CEOs, people that had achieved incredible things in their lives, things that clearly took an extraordinary amount of intelligence, willpower and hard work. Yet the one thing that none of them could manage to control was weight. Many had lost weight successfully in the past, and people told stories about losing 20, 30, 40kg which then crept back on despite their best efforts.
And I remember sitting there thinking “if all these incredible, intelligent, hard-working people can't manage to lose weight and keep it off, there must be something else going on underneath”. And this was really the seminal experience that led me to apply for a PhD working on diet and appetite regulation about two years later.
Some of the pathways involved in appetite regulation. Basically PYY, GLP-1 and OXM are hormones that signal to the brain “I’M FULL UP”; ghrelin is the hormone that tells your brain “I’M HUNGRY”. It’s thought that all these signals converge on the hypothalamus to regulate your appetite. Taken from an oldie but a goodie: Gut hormones and the regulation of energy homeostasis.
So why is it important to understand the role of appetite hormones in body weight regulation? Because it enables you to understand that biological signals drive you to eat without you even being aware of it. Here are some examples:
If you infuse ghrelin (the I’M HUNGRY hormone) into people (in a blinded study so people didn’t know if they were getting ghrelin or saline), they eat more.
An infusion of GLP-1 (an I’M FULL UP hormone) decreases food intake by 27%
A combination of GLP-1, PYY and OXM (all I’M FULL UP hormones) decreases food intake by 32%.
The potent effect of appetite hormones on food intake (and subsequent weight loss) is demonstrated by the holy shit how much weight did people lose results of semaglutide (GLP-1 agonist) trials:
What does all this data tell us about what makes dieting so difficult?
ALL HAIL ONE OF THE GREATEST STUDIES OF ALL TIME.
In this study, they measured the appetite hormones of a group of people with obesity before they lost 10kg, immediately after achieving 10kg weight loss, and then about a year after they had lost weight.
And just look what happens to the appetite hormones: weight loss reduces the concentration of the EAT LESS hormones and increases the concentration of the I’M HUNGRY hormone. And some of these changes persist a year after people had met their weight loss target.
To summarise:
Add this to the fact that weight loss also produces a larger-than-expected reduction in energy expenditure which also persists for at least a year after a person has lost weight, and then you realise that it’s actually pretty amazing that [a minority of] people can and do lose a lot of weight and keep it off long-term.
To end:
*I don’t known man, maybe they have tried that already.
**They really should have advisors who do research on this stuff though and if they haven’t been briefed, maybe don’t voice your feelings on the matter?
***Government advisors really should know this stuff.