Always exercising but without results? A study of 500 volunteers found that a fifth of us have inherited the 'unfitness gene'. As well as having significant impact on our aerobic fitness, our genetic makeup also affects our ability to burn fat through exercise.

If you often feel bloated, your body could be struggling to metabolise a food it is sensitive to, causing weight gain and fluid retention. Wheat and dairy products are often to blame.

Do you suffer with cold hands, dry hair and constipation - and feel irritable, depressed and tired? These are all symptoms of hypothyroidism – which can also cause weight gain.