Photo by Alexandru Acea on Unsplash
In short: A crash diet asks your body to live on far less food than it needs. Your body responds by protecting itself: it slows down, takes what it needs from your muscles and turns up your hunger, while your mind becomes tired, irritable and fixed on food. That’s why the weight so often comes back once the diet ends. Regular, nourishing meals and small changes you enjoy do far more for you, especially in midlife.
A wedding in six weeks. A summer holiday. A photo you didn’t like. Or simply a Monday morning when you’ve had enough. So you start: soup only, or shakes, or nothing after lunch, or a cleanse that promises a “new you” in ten days. The first few days feel almost exciting. The scale moves. Then you start feeling cold. Your head aches. You snap at people you love. You dream about bread. And one evening, without quite deciding to, you eat everything in sight.
Perhaps you’re thinking: “But I’ve tried everything else, and nothing seems to work.” I understand that frustration so well. I want to explain what really happens in your body and your mind during a crash diet, because once you understand it, you can stop blaming yourself, and start doing something kinder that actually lasts.
What is a crash diet?
A crash diet is any way of eating that cuts your food down drastically to lose weight quickly. It comes in many disguises: plans that allow only a tiny amount of food, meal replacement shakes, juice or soup “cleanses”, “detox” teas, cutting out whole food groups overnight, skipping meals, or pills that promise miracles. They all have one thing in common: they give your body much less than it needs, for the sake of speed.
Some people do follow a specific eating plan for medical reasons, under the supervision of their doctor. That’s a different situation. Here I’m talking about the quick fixes we impose on ourselves.
Why are crash diets so tempting?
Because they promise something we all long for: a fast answer. When you feel uncomfortable in your body, waiting feels unbearable, and a plan with clear rules feels safe. Advertising knows this very well. And for a few days, a crash diet seems to deliver, which makes it all the more convincing.
There’s no shame in having tried them. Most of us grew up surrounded by diet messages, and many women have been on and off diets for most of their adult lives. I wrote about why I stopped believing in them in Let’s talk about diets.
What happens to your body on a crash diet?
Your body is wonderfully clever, and its first job is to keep you alive. When food suddenly becomes scarce, it doesn’t know that you’re trying to fit into a dress. It thinks there’s a famine, and it reacts accordingly.
It saves energy. You feel colder, slower and more tired. Your body quietly turns down everything it can, a bit like a house where someone goes round switching off the lights.
It takes from your muscles. Much of what you lose quickly is water and muscle rather than fat. Muscle is precious: it keeps you strong and steady, protects your joints and uses energy even while you rest. Losing it makes the next diet even harder.
It runs short of nourishment. When you eat very little, or cut out whole groups of foods, it’s very hard to get everything your body needs. Many people notice dull skin, brittle nails, hair falling out, constipation, headaches, dizziness or poor sleep.
It turns up your hunger. Your body sends stronger and stronger hunger signals, and takes longer to feel full. Your body is trying to save you.
What does a crash diet do to your mind?
This is the part people talk about least, and I think it matters most. A hungry brain becomes obsessed with food. You think about your next meal while you’re still eating this one. You read recipes you won’t let yourself cook. You become irritable, anxious, low or simply flat.
Then comes the guilt. When the diet breaks, as it almost always does, you blame yourself. You feel weak, ashamed and further from your body than ever. Over time, this cycle can make your relationship with food and with your body very painful, and for some people it can grow into an eating disorder. If you’d like to start healing that relationship, Your body, your story is a good place to begin.
Why does the weight come back after a crash diet?
Because when the diet ends, your body is still in famine mode. It has slowed down, it has less muscle, and its hunger is turned up high. So when you start eating normally again, it stores what it can, as fast as it can, in case the famine returns. Many people end up back where they started, or a little above, with less muscle than before. And then the next diet begins.
This is the yo-yo so many women know by heart. None of it is a failure of character: your biology is simply doing its job. I explain how eating too little affects energy and muscle in more detail in Why you need more food, not less.
Are crash diets riskier after fifty?
I believe they are. From midlife, and especially around menopause, we naturally lose a little muscle and bone strength each year unless we look after them. A crash diet speeds that loss up, just at the moment when you most want to keep everything you have. Strong muscles and bones are what keep you climbing stairs, carrying shopping and gardening with ease for years to come.
Many women also find that poor sleep and stress make weight harder to shift in midlife, and a crash diet adds even more stress to the body. I wrote about this link in The direct impact of sleep and stress on your weight.
What helps?
When someone comes to me after years of crash diets, these are the steps I usually suggest.
1. Feed yourself properly again
This always comes first. Three real meals a day, and a snack if you’re hungry. A breakfast that lasts, like eggs, or yoghurt with walnuts and an apple. A proper lunch, perhaps a bowl of lentil and vegetable soup with bread and a piece of goat’s cheese. A calm dinner at the table. It may feel frightening at first. Give your body a few weeks to trust that the famine is over.
2. Put some protein on every plate
Protein helps you feel satisfied for longer and helps protect your muscles. A palm-sized piece of fish, chicken or tofu, a couple of eggs, a bowl of lentils or chickpeas, some yoghurt or cheese. Add plenty of vegetables, healthy fats like olive oil and nuts, and carbs you enjoy.
3. Change one small thing at a time
Instead of overhauling your whole life on a Monday, choose one small change and let it settle before adding the next. Water instead of a sweet drink at lunch. A short walk after dinner. Fruit in your bag for the afternoon. Small changes feel almost too easy, and that’s exactly why they last. I wrote about making habits stick in I want to change, but…
4. Move in ways you enjoy
Movement doesn’t have to be a punishment for what you ate. Try different things until you find something you look forward to: yoga, dancing, swimming, walking with a friend, lifting weights. If you can, include something that makes your muscles work, because strength is your best friend as the years go by. More ideas in Let’s talk about exercise.
5. Look after your sleep and your stress
A tired, stressed body is a hungry body. Protect your sleep, and give yourself little moments of calm during the day: a few slow breaths, time in nature, a creative hobby, a few minutes of mindfulness. They’re part of eating well, just as much as what’s on your plate.
What doesn’t help?
“Just one more” crash diet. Each new round tends to cost more muscle and more confidence.
Making up for a big meal by not eating the next day. It restarts the famine signal and the cycle with it.
Products that promise to melt, flush or detox. Your liver and kidneys do that work every day; they need regular meals, water and sleep, not teas and pills.
Judging yourself by the scale every morning. How you feel, sleep and move tells you far more.
Try this for one week
For seven days, eat three meals a day at roughly regular times, each one with some protein and some vegetables. Don’t weigh yourself this week.
Each evening, note three things in a notebook: your energy, your mood and how much you thought about food that day.
At the end of the week, read it back. Many people are surprised to see that when they eat more regularly, they think about food less. That’s your body starting to relax, and it’s the beginning of something that can last.
Frequently asked questions
Why do crash diets not work in the long term?
Because your body treats sudden, severe restriction as a famine. It saves energy, takes from your muscles and turns up your hunger, so the weight usually comes back once you start eating normally again.
Can a crash diet damage my health?
It can. Eating far too little can leave you tired, cold and short of nourishment, cost you muscle and, over time, harm your relationship with food. Some people notice hair loss, dizziness, headaches or digestive problems.
How do I stop the yo-yo dieting cycle?
Start by eating regular, satisfying meals again, with protein and vegetables at each one, and make small changes you enjoy rather than drastic ones. Looking after sleep, stress and movement helps your body settle too.
When should I talk to my doctor?
Please talk to your doctor before making any big change to how you eat if you have a health condition or take regular medicine, and if you’ve been on a very restrictive diet and feel dizzy, faint, unwell or very tired. If food, weight and guilt fill your thoughts or eating feels out of control, your doctor can help you find the right support.
Would you like some help?
Leaving crash diets behind is so much easier when you’re not doing it alone, and when someone helps you trust that eating properly is safe. That’s very much the spirit of my group programmes in nutrition and health, such as Six Tuesdays in Montignac. If you’d like to hear when the next group opens, write to me at hello@catherinepolet.coach.
If you’d rather have support that fits your body and your history one to one, I also coach online. Book a free 20-minute call, and we’ll talk about what a calmer, kinder way of eating could look like for you.
About Catherine
I’m Catherine Polet, a holistic nutrition health coach, yoga and autogenic training teacher for more than 30 years, author and speaker. I help people find a way of eating and living that suits their own body, online in English, French, Spanish and German, and in person in Southwest France.
