The weight gain and metabolism myth
It’s a common assumption: if you’re gaining weight, your metabolism must be slow. In reality, weight changes are rarely caused by metabolism alone. While calorie intake and activity levels definitely play a role, the body’s hormonal environment has a profound influence - and it’s often overlooked.
Hormones act as regulators for how your body uses energy, stores fat, and responds to appetite cues. Thyroid hormones, for example, control metabolic rate. When thyroid function is impaired, even mildly, energy levels can drop, and weight management becomes more challenging. Similarly, insulin - the hormone that helps regulate blood sugar - can influence fat storage and appetite. Persistent insulin resistance can lead to weight gain even if you’re eating healthily and exercising.
Oestrogen, progesterone, and testosterone impact body composition. For women, fluctuations during perimenopause or menopause can shift fat distribution and make weight management feel more difficult. For men, declining testosterone levels can reduce muscle mass, slowing metabolic efficiency and altering fat storage. Cortisol, the stress hormone, is another factor; chronically elevated cortisol can increase appetite, promote abdominal fat, and interfere with sleep, creating a cycle that makes weight gain much more likely.
It’s important to remember that weight gain is rarely caused by a single factor. Sleep disruption, chronic stress, gut health, and even prior dieting patterns can all influence hormones and, by extension, body composition. Simple blood tests and clinical evaluation can help to identify underlying hormonal contributors, allowing for targeted interventions rather than guesswork or “one-size-fits-all” advice. My approach is about looking at every angle, so I look at my patients’ lifestyle closely - not just blood tests and scans.
The really important thing I stress to patients is that weight changes - particularly those around perimenopause and menopause - are not some sign of failure! Hormonal imbalances are common and treatable. With the right approach - which may include lifestyle adjustments, stress management, and, where appropriate, targeted hormone therapy - it is possible to restore balance, improve energy, and support sustainable weight management.
Understanding the complex interplay between hormones and metabolism is often the first step toward regaining control and feeling confident in your body again. If weight gain has felt inexplicable despite your best efforts, exploring your hormonal health with a specialist will often provide some clarity and insight.