Why can't I lose weight (even though I try everything)

It's not your willpower: it's your physiology

If you've spent years trying to lose weight without success, you're probably blaming yourself for something you don't fully control. Body weight is regulated by a complex system of hormones, hunger and fullness signals, sleep and genetics. When that system is out of balance, eating less and moving more stops working the way the magazines promise.

The good news is that almost all of these causes can be identified and treated. The first step isn't another diet, but understanding what's happening inside your body.

The 7 most common medical causes

• Hypothyroidism: an underactive thyroid lowers energy expenditure and makes weight loss harder.
• Insulin resistance and prediabetes: the body stores fat more easily.
• Polycystic ovary syndrome (PCOS): very common and often undiagnosed.
• Sleep deprivation: sleeping less than 6 hours disrupts appetite and increases hunger.
• Chronic stress: raised cortisol promotes abdominal fat.
• Medications: some antidepressants, corticosteroids or antihistamines cause weight gain.
• Adapted metabolism: after years of dieting, the body reduces its expenditure to protect itself.

You don't need all of these causes to be stuck. Often one or two are enough to make losing weight an uphill battle no matter how hard you try.

The effect of previous diets

Every very restrictive diet you do leaves a mark. When you eat too little for weeks, your body interprets it as scarcity and slows down: you burn less at rest, feel hungrier and, as soon as you go back to eating normally, regain the weight with interest. This is the famous rebound effect, and it's biology, not weakness.

Most people who lose weight on strict diets regain it within a few years. The problem isn't you: it's the method.

What to do from now on

• Ask for a blood test that includes thyroid (TSH), glucose and insulin.
• Review with a doctor the medications you take in case they affect your weight.
• Prioritise 7–8 hours of sleep: it's one of the most underrated factors.
• Forget crash diets; look for a sustainable, supervised plan.
• Consider whether a medical treatment (such as a GLP‑1) makes sense in your case.

At DoctorLife, a free medical assessment is designed for exactly this: to rule out treatable causes, understand your history and design a plan built around your body, not around a brochure.

Frequently asked questions