More than 60% of women in relationships do not feel comfortable eating in front of their partner and almost half get shy when undressing, new research suggests. Of the 5,000 people surveyed, two-fifths of women feel like they are always dieting or are constantly concerned about their weight.

Differences between male and female attitudes towards sex and food are also apparent, with a quarter of women thinking about food every 30 minutes but just a 10th thinking about sex as often. On the other hand, men think about sex much more frequently, with one in 20 thinking about it every minute and 36% fantasising every half an hour.

Women also appeared to be concerned with dieting when eating out, with 13% of those questioned having chosen low calorie foods in restaurants instead of what they really wanted. Nutritionist and behavioural therapist, Mary Strugar, said: "The role of appetite is key to weight loss and a detrimental cycle of food restriction that causes hunger pangs may lead directly to overeating. "This is often called yo-yo dieting and is a reason why many people simply give up and break their diets early."

Many women admitted falling into this pattern, with 15% eating junk food in secret and one in 10 lying about doing so. Some 40% of women also have a passion for chocolate and eat it four times a week. Ms Strugar said the survey, carried out for Shapesmart, shows people need to face-up to their vulnerabilities.

She said: "You need to be realistic about your personal diet weaknesses and at the same time, try to swap high fat and sugary foods with slow release energy rich foods such as brown rice, sweet potatoes and bananas that will leave you feeling satisfied for longer and control your guilty cravings."