Do you have days where you feel fat although your clothes still fit as before? It could be all in your mind. New research has shown that the way we think can severely alter our self-perception.

When I wake up I always grope my tummy to assess its size. I know I'm not alone in doing this. But how come, even while I reach for a size 12 skirt, sometimes I feel enormous and sometimes I feel okay (though I usually think I could do with shedding half a stone)?

My friend Jules knows what I mean. She used to be a size 22 and has now slimmed down to a 12, yet says she still feels fat. "Even though the evidence of my weight loss is in front of my eyes on the scales and in my wardrobe, I am still in "fat girl" mentally"

Jules's situation shows that how we feel in terms of our size isn't necessarily a true reflection of how we actually are. That sensation of being too fat (or too thin) could all be in your mind. The latest research from the University College London suggests that our perception of size is a sensory illusion created in our brain. This study made volunteers believe their waists were shrinking as they touched them through a clever vibrating device, which interfered with the sensory map that helps the brain accurately perceive size. The high levels of brain activity in one region showed that it creates an illusion of the perceived body size, based on the sensory information it is receiving.

These findings are a step towards expanding our understanding of eating disorders such as anorexia, where people are obsessed with their weight, and conditions like Body Dysmorphic Disorder (BDD), a type of Obsessive Compulsive Disorder where people become preoccupied with an imagined or actual defect in their appearance.

If you fit into your jeans OK then maybe feeling fat is all in your mind. Eating a nutritionally-balanced diet and getting plenty of sleep and exercise increases the chance of being confident about the way you look, while focusing on the things that make you happy builds self-esteem.

However, if you continue to be dissatisfied with your weight and it is within the normal range for your height, then it's worth looking at why this might be. If you think your concern with your size or body could be a problem, then do seek advice.