"I'm eating less and I'm exercising — but the scale simply won't budge." If you're reading this, I'm willing to bet you've said that to yourself more than once. So why do we really struggle to lose weight? Here's the heart of it: it's usually about far more than "eat less, move more." Let's walk through five of the most common reasons, in the light of current research.
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1. Medical checks and hormones
The place to start is a blood panel. If no one has looked at your fasting insulin, your three-month blood-sugar average (HbA1c) and your fasting glucose, an overlooked insulin resistance could be part of the picture — and that can make your body resistant to losing weight, too. Low iron, B12 or vitamin D slow your energy production, deepen fatigue and drag down your workout performance. The thyroid deserves particular attention: alongside T3 and T4, it's worth checking thyroid antibodies (anti-thyroglobulin and anti-TPO), because an underactive thyroid can make weight loss feel almost impossible. In women, the estrogen–progesterone balance matters enormously; when it shifts around menopause — which can begin earlier than many expect — weight control gets harder. And then there's sleep: too little of it disrupts leptin and ghrelin, the hormones that govern appetite. So if you're eating carefully and moving plenty but sleeping poorly, it's no surprise the scale is stubborn.
2. Digestion and the gut microbiome
The second key piece is gut health. Frequent constipation, gas, bloating or constantly needing the loo can all be your gut signalling that something's off. Your gut bacteria are surprisingly influential in weight regulation — certain species, such as Akkermansia and Bifidobacterium, are linked to healthier metabolism. If you want these friendly bacteria to settle in and stay, invite whole grains, fermented foods and plant-based foods to your table more often.
3. Personalised nutrition
Third is your eating pattern itself. Low-carb, high-protein and ketogenic diets are everywhere — but they don't produce the same result in everyone. Your genetics and your microbiome might actually do better on a lower-fat or more vegetable-forward way of eating. The idea gaining ground in recent years — "precision nutrition" — captures exactly this: rather than one template for all, a plan fine-tuned to you. It's why genetic testing and microbiome analysis are increasingly shaping the diet plans we build.
4. Energy balance and muscle
Fourth is the equation that looks simplest of all: the balance between the energy you take in and the energy you burn. Simple in theory, anything but in practice — because your basal metabolic rate, your muscle mass, your age, your stress levels and your sleep are all shifting that balance constantly. The research is clear: of two people eating the same calories, the one with more muscle burns more energy, even at rest. So if you want weight loss to come more easily, focus on building muscle through regular resistance (strength) training.
5. Monotony versus variety
Fifth is a detail most people miss: variety. It's easy to settle into the same four or five foods, but your gut bacteria crave diversity. Recent research shows that people who eat around 30 different plant foods a week have noticeably greater gut-bacteria diversity. Vegetables, fruit, legumes, nuts, seeds, whole grains, herbs and spices all count towards that 30. Adding colour to your plate supports both your microbiome and your weight-loss journey.
In short: not losing weight is never a one-line equation of "I ate less and moved more." From your hormones to your gut health, from your eating pattern to your sleep, many factors are in play. Simply recognising which of these you're wrestling with is the first step towards the right change.
This article is for general information and isn't a substitute for individualised advice from your own doctor or dietitian; any testing or treatment decisions should be made with them.
Merve Tığlı, Dietitian
Sources: American Gut Project (McDonald et al., 2018) — plant diversity and the microbiome; Taheri et al., PLOS Medicine (2004) — sleep, leptin and ghrelin; Depommier et al., Nature Medicine (2019) — Akkermansia muciniphila.