Social media encourages us to blame cortisol and insulin for that thickening middle, but are hormones really to blame? Sometimes, says Claire Turnbull, but it's complicated.
If you’ve been struggling to button up your jeans, your undies feel too tight, or your belt has gone up a notch, you might wonder what on earth is going on, especially if you don't really feel you've been eating more than usual.
Search this issue online, and hormones quickly appear at the top of the list of things to blame. Insulin ‘locking away fat’, cortisol creating a ‘stress belly’ and your appetite hormones being 'broken' are common claims.
But are hormones really responsible for changes in our weight, shape and size?
The answer? Kind of. But it’s not as simple as social media posts portray.
Hormones are chemical messengers that tell organs and tissues what to do. We have over 50 of them in our body and some influence our appetites, how we build and maintain muscle, and where or how readily we store fat. But while body fat is influenced by some hormones, fat tissue also produces hormones of its own. It can be a bit of a chicken-and-egg situation.
Let’s meet some of your hormones and find out more.
Insulin
Insulin is a hormone made in the pancreas, an organ that sits behind the stomach. When your body breaks down foods containing carbohydrates into glucose, insulin helps move glucose from your blood into your cells to be used for energy. It also helps store glucose as glycogen in your muscles and liver for later.
Your pancreas is super clever and adjusts how much insulin it releases in response to what you eat. The amount and type of carbohydrate you eat have a big influence, although protein and other factors also play a part. The aim is to keep the amount of glucose in your blood within a range of roughly 4 to 8 mmol/L.
This process, however, can be disrupted if your body becomes resistant to insulin. This basically means that your body no longer responds effectively to the insulin that you are producing, and the pancreas tries to compensate by making more insulin.
Over time, the insulin-producing cells in the pancreas may no longer be able to keep up. Blood glucose can then run consistently higher than it should, which can potentially lead to prediabetes and then for some people, type 2 diabetes.
In people with PMOS, formerly called PCOS, high insulin levels can stimulate the ovaries to make more androgens, such as testosterone and contribute to disrupted ovulation. Insulin resistance is part of the picture for many people, although not all, with PMOS.
There are many drivers of insulin resistance, but some of the main ones include genetics, medical conditions, excess fat stored around your abdominal organs, low levels of activity, low muscle mass, a pattern of eating dominated by highly processed, low-fibre foods, poor sleep, and certain medications.
Oestrogen
If, like me, you have reached midlife and feel your body has changed even though you are eating and exercising in much the same way, you are not imagining it. Even after 26 years in the nutrition and fitness game, I have started to notice my bra straps digging in!
Here’s why. During perimenopause, which commonly begins in the mid-forties, although it can start earlier, oestrogen levels can wobble all over the place before settling at lower levels after menopause. Menopause is confirmed when you have gone 12 months without a period, and the average age for that in New Zealand is 52.
Oestrogen influences where we store fat. As levels fall, fat is more likely to shift from the hips and thighs towards the middle, which is why your shape may change even if the scales have not moved much.
Oestrogen can also affect how sensitive the body is to insulin, which can add to the insulin resistance picture.
So yes, changing oestrogen levels may play a part in how your jeans are fitting, but there’s more going on than oestrogen alone. Another important factor is the natural loss of muscle mass that happens with age and can accelerate across the menopause transition. Muscle is important for strength and is one of the main places glucose is used and losing it can affect insulin sensitivity and body composition
This time of life is also a busy one for many women, who are often caring for children and/or ageing parents and juggling work or other responsibilities. Those pressures, combined with sleep disturbances, brain fog and mood changes that can come with perimenopause, can create something of a perfect storm.
Testosterone
Testosterone helps support muscle growth, strength, and bone health, and it also influences fat distribution. Levels tend to decline gradually in men from around the age of 30 to 40, although there is considerable variation. Ageing, health conditions, body fat, nutrition, sleep, and activity can all affect both testosterone levels and body composition.
Appetite hormones
Until recently, ghrelin and leptin were the appetite hormones most people had heard about. Ghrelin is made mainly in the stomach and tends to rise before meals, sending the ‘time to find food’ message. Leptin, on the other hand, is produced mainly by fat cells and tells the brain how much stored energy is available.
With the rise of medications such as Ozempic and Wegovy, the hormone GLP-1, which these drugs mimic, has also come into the spotlight because of the role it plays in appetite regulation.
These hormones, like others, are influenced by what and how we eat, while sleep and movement also affect appetite regulation. Although we cannot simply reset them, healthy habits can help support our natural hunger and fullness signals, making it easier to regulate how much we eat.
Cortisol
Social media would have you believe cortisol is making you fat, and that a special cortisol diet, supplement or cleanse is the answer.
Cortisol, however, is not the enemy it is being made out to be. Made by your adrenal glands, it helps regulate blood pressure, inflammation, your sleep-wake cycle, and makes fuel available during stress.
Rare medical conditions can cause abnormally high cortisol levels, while prolonged use of some steroid medicines can mimic its effects, leading to weight gain around the middle and other symptoms. This is very different from being stressed by your inbox, finances, or family life.
Ongoing stress can still make managing weight harder. It can disrupt sleep, pull us towards comfort food and alcohol, and leave us with less energy to move or cook. Cortisol may be part of that chain reaction, but it is rarely the whole story.
And what about the thyroid?
An underactive thyroid can contribute to weight gain, usually alongside tiredness, constipation, dry skin, and feeling unusually cold. If this sounds familiar, see your GP rather than trying to ‘boost’ your thyroid with supplements.
Five simple ways to support hormones and a healthy weight
1. Protect your sleep, because it really matters. Aim for a fairly regular bedtime and wake time, and give yourself enough opportunity to sleep – for example, if you know you need to read for an hour before you fall asleep, you'll need allow nine hours in bed to get an eight-hour sleep. Regular, good-quality sleep supports appetite regulation, insulin sensitivity and blood sugar control, overall energy and decision-making.
2. Avoid saving most of your food for late at night. You do not need an extreme fasting window, but for many people it is better to avoid eating too much close to bedtime because the body generally handles glucose less effectively during the biological evening and night. Spreading more of your food across the day may help. Making lunch more substantial or having a planned afternoon snack can also help if you often arrive home in the evening ravenous.
3. Use your muscles. Muscles are like a glucose sponge. When working, they take up glucose with much less help from insulin. A 10-minute walk after a meal, regularly breaking up sitting and doing strength exercises a couple of times a week all count.
4. Choose better carbs, not no carbs. Oats, beans, lentils, whole grains, fruit and starchy vegetables bring fibre and nutrients. Pair them with protein and colourful vegetables. Aim for half a plate of vegetables, a quarter protein and a quarter quality carbohydrate as a starting point for lunch and dinner.
5. Try to dial down your stress volume in ways that work in real life. Slow, controlled breathing, increasing how much you move, spending more time outside, taking proper breaks (even short ones), prioritising connection and saying "no" occasionally can all help. The best strategies are the ones you can repeat over and over again.
So, are your hormones to blame for your weight gain?
They may be contributing, particularly if there is a genuine medical condition. But, more often, they are one part of a much bigger conversation involving your genes, life stage, muscle, body fat, sleep, stress, food environment, and daily habits.
I think it is always important to remember that, when it comes to health challenges, your body is never trying to deliberately work against you. It is just responding to the messages it receives.
Some illness and physical changes are outside our control, but if we change those lifestyle factors that within our control, our body will respond positively.
Claire Turnbull is a registered nutritionist with an honours degree in dietetics, a wellbeing educator and author.
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