How hormones can affect your weight

Hormones are chemical messengers that regulate almost every function in your body, including your metabolism, appetite, how much fat you store and energy levels. When they’re out of balance, you can gain weight, even when your diet and exercise habits have not changed.

When your body stops responding properly to insulin, it makes more of this hormone, which can cause extra sugar in the body to be stored as fat, increase cravings for sugary foods and lead to further weight gain.*

Cortisol, the stress hormone, stimulates appetite and increases intake of highly palatable foods.

For men, declining testosterone levels (which drop naturally from around age 30) reduce muscle mass and slow metabolism, making it easier to gain weight.**

For women, the decline in estrogen during perimenopause and menopause shifts fat distribution from the hips and thighs to the abdomen, increasing metabolic risk.***

An underactive thyroid also causes weight gain. This is because low thyroid levels cause your body to hold on to more salt and water, it slows down your metabolism, and can lead to food cravings and increased appetite. Most people gain between 2–4.5 kg but women who have had low thyroid levels for a long time can gain more.****

Understanding your hormones is about understanding your body so you can work with it, not against it.