As the weather cools and we start thinking about shedding those extra winter kilos, it’s tempting to look for a quick fix. Crash diets and rapid weight loss programs are everywhere—promising a slimmer, healthier you in just a few weeks.
But before you sign up for the latest fad, it’s worth asking: could these diets be doing more harm than good?
According to nutrition expert Maria AbiHanna from Food Label Maker, the answer is a resounding yes. ‘People blame willpower when they can’t stick with a diet,’ she says. ‘The truth is that your body is built to resist rapid fat loss. So, the key is working with your biology, not against it.’
Let’s take a closer look at five surprising ways crash diets can backfire—and what you can do instead to achieve lasting, healthy weight loss.
1. Your brain interprets dieting as danger
When you suddenly slash your calorie intake, your body doesn’t see it as a positive change—it sees it as a threat. Your brain’s energy regulator responds by lowering your metabolism and ramping up hunger signals.
This is your body’s way of protecting itself from starvation, and it often kicks in before you’ve even lost much weight. The result? You feel hungrier, more tired, and less motivated, making it almost impossible to stick to your plan.
What to do instead: Try calorie cycling. This means eating a little more on days when you’re active and a little less on rest days. It helps keep your metabolism humming and prevents your body from going into ‘energy conservation’ mode.
2. Your gut health takes a hit
Many quick-fix diets cut out entire food groups—think carbs, dairy, or fats. While this might seem like a shortcut to weight loss, it can wreak havoc on your gut health.
A diverse diet is essential for a healthy microbiome (the community of good bacteria in your gut), which plays a crucial role in how your body stores fat and uses energy.
What to do instead: Aim for variety! Try to eat at least 30 different whole foods each week—leafy greens, legumes, nuts, herbs, whole grains, and more. The more diverse your diet, the healthier your gut—and the easier it is to maintain a healthy weight.
3. Blood sugar rollercoaster
Juice cleanses, meal replacement shakes, and other ‘miracle’ diet foods often cause your blood sugar to spike and then crash. This leaves you feeling tired, irritable, and craving more sugar—a vicious cycle that can sabotage your weight loss efforts.
What to do instead: Start your meals with healthy fats or fibre-rich foods, like avocado, chia seeds, or leafy greens. These slow down digestion and help keep your blood sugar stable, so you feel fuller for longer and avoid those energy crashes.
4. You might feel colder and hungrier
Did you know that losing weight too quickly can actually make you feel colder? That’s because rapid weight loss can reduce the activity of brown fat—a special type of fat that helps keep you warm and burns calories. When brown fat activity drops, you may feel cold, fatigued, and even hungrier than before.
What to do instead: Focus on slow, steady weight loss. Stay active and avoid extreme restrictions to preserve your brown fat and keep your metabolism working efficiently.
5. Your hunger signals get out of whack
Extreme diets often require you to ignore your body’s natural hunger and fullness cues. Over time, this can dull your ability to recognise when you’re actually hungry or satisfied, making it harder to maintain a healthy weight in the long run.
What to do instead: Practice structured, flexible eating. Eat at regular intervals and pay attention to how different foods make you feel, not just how many calories they contain. This helps you rebuild trust with your body and makes healthy eating more sustainable.
As Maria AbiHanna points out, ‘Most quick-fix diets fail not because people lack discipline, but because they ignore basic physiology. If you focus on preserving muscle, regulating blood sugar, and protecting gut and hormonal health, weight loss becomes not just possible, but easy.’
While quick-fix diets may seem appealing, it’s worth considering the potential long-term effects on your overall health and well-being. As always, it’s important to find an approach that works for your body and lifestyle.
What are your thoughts on rapid weight loss plans? Have you ever tried one, or do you prefer a slower, more balanced approach? Share your thoughts and stories in the comments below.
Also read: Why most people are picking the wrong diet—here’s what a top dietitian recommends instead
