SARAH DI LORENZO: Why weight gain happens and the three proven habits to help stop yo-yo dieting

In my clinical practice I have sat across from thousands of women and men who have lost the same 10, 15 or 20 kilograms multiple times over. They are not lazy. They are not undisciplined. They are not failing because of a character flaw. They are caught in a physiological trap due to diet culture and sadly most conventional weight loss advice does almost nothing to help them get off this rollercoaster.

Diet culture offers a short-term solution, so many at the end of their weight loss journey went back to their “normal” eating habits because they viewed the diet as abnormal. This is what needs to change, a new normal needs to be created.

Yo-yo dieting which is the cycle of restriction, weight loss, rebound, and restriction again, is not a motivational problem. It is a biological one. And understanding biology is the first step towards ending the cycle permanently.

When caloric intake drops significantly, as it does on most conventional diets, the body responds with a sophisticated and powerful set of survival adaptations designed to protect against starvation. Resting metabolic rate decreases as the body becomes more energetically efficient.

Ghrelin, our hunger hormone, will rise significantly and remain elevated for months to years after weight loss, driving persistent hunger that most people interpret as weakness but is in fact a measurable hormonal signal. Leptin, our satiety hormone produced by fat cells, falls as fat mass decreases, reducing the brain’s sense of fullness and increasing the drive to eat.

Muscle mass is lost alongside fat during caloric restriction and particularly when protein intake is inadequate, and this loss of metabolically active tissue further reduces the number of calories the body burns at rest. Muscle is so important for regulating our blood glucose, think of it like a glucose disposal in our bodies.

The result of all of these adaptations is what researchers call metabolic adaptation, so the body now requires fewer calories to maintain its current weight than it did before the diet. This is why the same caloric intake that produced weight loss in week two of a diet produces a plateau by week eight, and weight regain the moment restriction is relaxed even slightly. This is not failure. This is your body doing exactly what it evolved to do, and fighting it with more restriction simply deepens the adaptation.

The research is consistent and clear that the dietary patterns that produce weight loss that is maintained over two, five, and 10 years are built on three non-negotiable principles that conventional dieting almost universally ignored and are key to long-term success.

The first is adequate protein. Research and in my clinical practice show that higher protein intakes are associated with significantly greater weight loss maintenance at 12 months and beyond, not just greater initial weight loss.

The mechanisms are multiple and well-established. Protein preserves the lean muscle mass that determines resting metabolic rate, this means metabolism does not drop as dramatically during weight loss when protein is adequate. Protein produces the strongest and most sustained satiety response of any macronutrient because it suppresses ghrelin, stimulating GLP-1 and PYY, and reducing total caloric intake through genuine hormonal satiety rather than willpower.

And protein has the highest thermic effect of any macronutrient, this is approximately 25 to 30 per cent of protein calories are used in the digestion process itself, providing a meaningful metabolic advantage over equivalent calories from fat or carbohydrate.

The target is 1.2g to 1.6g per kilogram of body weight daily and this needs to be distributed across every meal, starting with breakfast, not just at dinner as many do.

The second is dietary fibre. A high-fibre diet sustains the gut microbiome diversity that regulates appetite hormones, produces the short-chain fatty acids that support insulin sensitivity and fat metabolism, and maintains the gut barrier integrity that keeps systemic inflammation, which is itself a driver of weight regain, within a healthy range.

People who increase dietary fibre consistently lose more weight, regain less of it, and report greater satiety than those on low fibre matched for calories.

Many people fear fibre because of the popularity of low carb diets. This way of thinking needs to change.

Try to eat 30 or more different plant foods per week including vegetables, fruit, legumes, whole grains, nuts, seeds, herbs and spices. This is the target that the research consistently supports for the microbiome diversity most protective against weight regain.

The third is sustainability over perfection. The diet that works is the one you can maintain without suffering and not the most aggressive restriction, not the most dramatic results in the shortest time, but the eating pattern that you can live within for years, that keeps you satisfied and nourished, and that supports the muscle mass, the gut health, and the hormonal environment that make long-term weight maintenance physiologically achievable rather than physiologically impossible.

My tips are to stop counting calories and start building meals. Every meal around a protein source and a fibre source before anything else. Stop restricting and start nourishing.

Eat in line with your circadian rhythms and make dinner your smallest meal.

Start treating your body as a system that responds to being well-fed with protein and fibre diversity in ways that restriction never can.

The body that is adequately nourished is a body that stops clinging to fat stores, stops producing excessive hunger signals, and stops fighting every attempt you make to reach and maintain a healthy weight.

This is the key to stop yo-yo dieting.