A brief overview of some of the hormones that contribute to making us hungry.
If you’re anything like me, when you’re hungry you let EVERYONE know about the fact. We often talk about feeling hungry and how it is associated to our mood or our current state of health. The press is constantly going on about feelings of ‘hangriness’ or how during the menstrual cycle or menopause many turn to food. But just why do we get hungry? The answer is down to hormones. However, the answer is incomplete, as many scientists still haven’t fully worked out the relationship between feeling hungry and the balances of different hormones. In this blog post, I’ll briefly summarise the absolute basics of what we do know about the relationship between hormones and hunger.
The hormone which is currently taken to be the main “hunger hormone” is ghrelin. As a side note, I personally think this is a really cool name for a hormone because it sounds a bit like gremlin, and it could be argued that I turn into one of those when I’m very hungry. Anyway, ghrelin is the hormone which is released from your gut when the stomach is empty – it stops being secreted when the stomach is full. This is what triggers your stomach to rumble and you to seek out food. It is also linked to body weight – the lower your weight is, the more ghrelin is in your blood in order to try and build up your body mass. Ghrelin doesn’t work on its own, it stimulates a range of other chemicals in your body to work, and these all contribute to the effects which are seen. The effects of ghrelin are counteracted by the hormone leptin, which is released from fat cells when you are ‘full’ and inhibits the responses which ghrelin triggered.
The specific relationship between hunger hormones and those involved in the menstrual cycle is murky at best, and a grey-area of research. I spent a while looking through academic databases for any promising research into this area (look at the effort I put in for you, dear readers!) and didn’t actually find all that much to go on. There have been a few studies into this topic, which have some results which appear to make sense. But the problem is that multiple factors have to be taken into consideration (such as the links to emotion and activity during various phases of the menstrual cycle, and the fact that much of the research has had to be carried out using laboratory models rather than humans).
However, the consensus at the moment tends to be that at various phases of the menstrual cycle, appetite does change. It also appears to be linked to levels of hormones which promote satisfaction and other such emotions (hunger hormones are also linked to emotional responses – it is thought that some obese people continue eating due to insensitivity to the hormones which make you feel satisfied and content after having an ‘average’ sized meal). Thus, during the menstrual cycle, binge eating is linked to the time when secretions of these hormones are lower – this could therefore also be linked to why people report mood swings during different stages of this period.
Even less is known about the links between hunger and the phases of the menopause, but again the current scientific idea is centred around the decrease in hormone levels that occurs during this time period. It is almost certainly the drop in hormone levels during this period that leads to increased weight post-menopause: the lower metabolic activity associated with the reduced hormone levels means that less food is used for energy and so is stored as fat. So just because you’ve put on a few extra pounds post-menopause, it doesn’t necessarily mean you should dash off down to your local slimming group – just consider what you’re eating and try not to overeat very often.
So that’s all I can say about this topic for now, folks! I do like to keep my eye out for scientific developments, and if any ground-breaking research happens linked to this matter, I will definitely write another blog post about it, if that’s something people would like to see. Do let me know if there’s any other burning biological questions you’d like to know the answer to, and I’ll see what I can do to explain it in the most non-nonsense way possible!
If you’re interested in finding out a bit more, the BBC have a nice summary of hunger on their archived iWonder page here.
This post was loosely inspired by something I saw on twitter – you can follow me here.