Broken metabolism, appetite hormones and how to avoid weight gain
“I only need to look at food and I gain weight”
“I eat considerably less than my husband, but he is thin, and I keep on gaining weight”
“I can lose weight, but then it piles back on whenever I stop starving myself” …
“Is my metabolism slow/ broken?”
If you have been struggling with trying to lose weight and have been on and off different diets but are finding yourself in a place not dissimilar where you started, you are not alone. Lots of women are struggling with a similar journey, often blaming themselves, stuck in the cycle of starting a new diet, exercise regimen or supplement regimen; it may work temporarily and then things go back to where they were, or worse when you consider lowered self-esteem, a feeling of hopelessness and often a higher weight than before. My clients often ask me whether their diet or lifestyle can have an impact on their metabolism. Or whether they have broken their metabolism in some way.
Can your metabolism be broken?
There are several things that can slow or speed up your metabolism, some of which you can change, and some you cannot. For example:
Your body size and muscle mass a larger body will require more energy. More muscle mass will use more calories.
Weight loss weight loss, especially when rapid, reduces metabolic rate.
Regularity of eating. Eating regularly, for example, every 3-4 hours increases your metabolic rate, whereas having long periods without food will decrease it (this is not to say that you should eat round the clock, there are benefits to fasting, especially in the evening and overnight!)
Movement Any structured and planned activities or things you might not think about in day-to-day activity, such as cleaning or gardening.
Dieting and food restriction trigger your body to conserve energy for another time. It is a survival mechanism of your body. It is very effective in noticing an energy shortage and will reduce your metabolic rate to save energy.
Life stage. Metabolic rate is higher during significant periods of growth and development, such as puberty and pregnancy, and reduces at menopause.
- Infection and illness when you are unwell, your body has a higher metabolic rate and energy needs to fight infection.
Metabolism is the process by which your body converts anything you eat or drink into energy that your body can use to do the wonderful things it does. However, when most people talk about metabolism, they mean the basal metabolic rate or the amount of energy a body uses at rest, like breathing, keeping your heart beating, regulating body temperature, for growth and repair, and brain and nerve function. Essentially, it is the amount of energy that your body needs to keep going.
The effect of weight loss and dieting on metabolism is more complex than may seem at first. It’s only recently that people started speaking about the risks of weight loss diets, like damaged relationship with food, menstrual irregularities, fatigue, constipation, headaches, and low mood. All of these ‘side-effects’ are relatively easy to recognise (see box below). However, many women ask me whether their previous dieting or future attempts will break their metabolism, because it’s not something that you can easily assess for or test. There is much more talk around this online, often in a language that can feel quite frightening. It raises this feeling of hopelessness and anxiety in people, especially those who are trying to lose weight upon advice from a doctor; they feel that they are doomed to “fail” whatever they do; they can feel like health and wellbeing is not accessible to them.
Menstrual irregularities, fatigue, low sex drive, dizziness and difficulties concentrating, insomnia, constipation, headaches, and low mood can all be signs that your metabolism has slowed down, but these can also be symptoms of other issues, for example, thyroid disease, polycystic ovarian syndrome or nutrient deficiencies]
A couple of studies published in 2022 closely monitored what happens to people when they lose weight, including how much fat and how much muscle is lost and what changes happen to their hormone levels and metabolism. They showed that if you lose approximately 10% of your weight, your body at rest needs on average 100 calories a day less to do what a body needs to do: breathe, keep the heart beating and moving blood around, and repairing tissues. I will give you an example to make this a little clearer: a person who weighed 80kg and lost 8kg is likely to need 100 calories less from food or to expend 100 calories more with activity to maintain this new weight than a person who has always been that weight. So dieting seems to impact the metabolism, but this effect reduces with time. Research shows that after about a month of stopping the diet, metabolism perks up a bit and the difference becomes even smaller, about 50 calories a day less than before the diet.
The slowing down in metabolism is due to a combination of two factors:
- with weight loss some muscle and some fat tissue will be lost and therefore these ‘lost’ tissues will no longer require calories
- calorie restriction leads to some changes in hormones, which then lead to slower metabolism.
This would be a relatively straight forward story, but when you look at the actual numbers rather than averages, it becomes clear that everyone’s body reacts so differently to dieting and weight loss. For example, for a handful of women dieting lead to faster metabolism, and at the other extreme, some experienced their metabolism plunge by 700 calories. So, although for the majority of women dieting will have a relatively small impact on the metabolism, for others it may mean significant changes in what they are able to eat in order to maintain the new weight.
The hormones that drive our hunger
Changes in metabolism, of course, it’s just one part of the complex picture. When you lose weight or are in the process of losing weight, your hunger goes up and your fullness signals tend to be delayed or blunted. These changes are driven by changes in fullness and hunger hormones. The hormone that increases hunger (ghrelin) goes up and the hormone that makes you feel full (leptin) goes down, even when a person is not restricting calories and eating seemingly ‘enough’. Our body is designed in a way that resists weight loss much more than weight gain. Research shows (and I see this a lot in my clinic) that people who lose weight and maintain it have something in common.
So, here are my top 3 tips on how to feel in harmony with your body and prevent weight regain!
- Being able to acknowledge successes and positive experiences Making lifestyle and dietary changes (and life in general!) can feel challenging at times. Most of us have an automatic draw towards food for self-soothing and comfort. Learning alternative coping mechanisms can be incredibly helpful but allowing flexibility around comfort eating without viewing it as a disaster or a reflection of your willpower/ worth is equally as important. Reflect in a balanced way and look back at the times where things didn’t go the way you wanted alongside the positive changes and efforts that you have made.
- Setting goals that are appropriate for you and maintaining motivation Goals that are challenging (but not challenging!) and continuous work to review progress and sustain motivation can be so helpful. If you can, find somebody (like me!) who can help you with this. Strategies like cognitive restructuring, behavioural contracting and problem solving can be so helpful in helping people feel positive and stick to the habits that promote health and happiness.
- Eating well, moving your body and learn how to rest…with ease and joyEating or exercising in a way that feels difficult and not enjoyable is not sustainable (and it shouldn’t be!). If you are trying a new approach with your eating, check whether it hits these two criteria: a) addresses your specific circumstances and conditions b) is easy to follow and enjoyable to do. Learning nutritional and lifestyle principles that will work best for you and how to incorporate these in your day to day with ease is not something that people learn in a week, so it can feel more challenging at the beginning. But it should get easier and eventually should start feeling like what you instinctively want to do.
Martins C., Bower B. and Hunter G (2022) Metabolic adaptation delays time to reach weight loss goals Obesity (Silver Spring) 30(2):400-406. Martins C., Roekenes J., Salamati S., Gower B., Hunter G. (2020) Metabolic adaptation is an illusion, only present when participants are in negative energy balance Am J Clin Nutr. 112(5):1212-1218
Wadden T., Considine R., Foster G., Anderson D., Sarwer D., Caro J. (1998) Short- and long-term changes in serum leptin dieting obese women: effects of caloric restriction and weight loss J Clin Endocrinol Metab 83:214–8.
Ramage, S., Farmer, A., Apps, E., and McCargar, L. (2013) Healthy strategies for successful weight loss and weight maintenance: a systematic review Applied Physiology, Nutrition, and Metabolism. 39(1): 1-20