Always wonder why your diet and exercise regimens never seem to work?

Possibly you’re unwittingly undoing your best efforts.

Last week, the British Nutrition Foundation identified more than 100 different factors that influence our weight.

However, many of the tips they offered – such as eating smaller portions and not relying on ready-made foods that are high in calories and fat – are fairly obvious.

Here you can find more surprising habits that are sabotaging your weight- loss regimen:

Look again at your shopping trolley

1. Eating cereal for breakfast. A U.S. study found breakfast cereal sweetened with sugar left overweight participants hungry before lunchtime, and they consumed more calories a day than those given an egg for breakfast (the protein kept them full). Egg eaters also had significantly lower levels of ghrelin, a hormone that stimulates appetite.

2. Having milk in your tea. Last year, Indian scientists found tea contains high levels of compounds, theaflavins and thearubigins, that help to reduce the amount of fat absorbed by the gut, and can cut cholesterol. However, proteins found in cows’ milk neutralize this ability. Drink your tea black.

3. Eating white bread. Too many refined carbs, especially white bread and white rice, can lead to weight gain, particularly around the midriff, found researchers at Tufts University in Boston.

Two groups ate roughly the same number of calories each day, but those who ate mostly refined carbs added a half inch on their waist per year compared with those eating unrefined “whole” foods such as vegetables and wholegrain bread.

4. Not reading food labels. A study in the Journal of Consumer Affairs showed that people who habitually read food labels as well as taking exercise lose more weight than those who merely exercise. What’s more, those who only read food labels and are sedentary lose more than those who exercise but ignore the food labels.

5. Drinking too much fruit juice. Fruit juices and other sugary drinks have a stronger impact on weight than calories from solid food, according to a study in the American Journal of Clinical Nutrition. Cutting out just one sugary drink a day resulted in a weight loss of more than 1lb after six months.

6. Underseasoning your food. Adding a bit of ground cayenne pepper to your meal can help burn calories faster. What’s more, the pepper seems to curb hunger – especially for fatty, salty and sweet foods, found nutritionists at Purdue University in Indiana.

7. Avoiding yoghurt. A study in the International Journal of Obesity found obese adults who ate three servings of fat-free yoghurt a day as part of a reduced-calorie diet lost 22% more weight and 61% more body fat than those who simply cut calories.

Yoghurt eaters also lost 81% more fat in the stomach area. It’s thought the calcium and protein in dairy products may help burn fat.

How friends ruin your plans

8. Overweight friends. If your friends gain weight, the chances are you will, too, according to a study from Harvard University.

“We find that having four obese friends doubled people’s chance of becoming obese, compared with people with no obese friends,” says Alison Hill, the study’s lead author.

Why? A recent Dutch study found that we tend to mimic each other’s behavior when we eat out, taking a bite at the same time.

9. Reading recipe books and magazines. Professor Kathleen Page, a psychologist at the University of Southern California, discovered looking at pictures of high-fat foods stimulates the brain’s appetite control centre, leading to an elevated desire for sweet and savory food.

10. Not chewing enough. The longer food remains in the mouth, the more chance the tongue has to send messages to the brain to release the necessary digestive juices. “Chewing and digesting solid food fills you up,” says dietitian Helen Bond.

11. Eating at work. Research shows we typically eat 30% more calories in company than when alone and that women at work are more likely to be influenced by the diet patterns of colleagues than men. In one study, female secretaries ate 5.6 times more chocolates if these were on a nearby desk of a colleague than if they had to walk two metres to get them.

12. Eating off the wrong-colored plate. A study from the Journal of Consumer Research found when food is on a plate that matches its color, it tends to blend into the plate, leading people to eat more. When the same amount of food is served on a plate that contrasts the meal, such as red spaghetti on a green plate, the portion appears larger and is more psychologically satisfying.

13. Not getting enough sleep. A study published in the journal Sleep last month suggested too little encourages the genes that cause weight gain. Longer (nine hours) suppresses the action of these “obesity” genes.

14. Dieting by yourself. A study in the journal Obesity earlier this year found that team-mates in a weight-loss competition significantly influenced each other’s weight loss. “We know that obesity can be socially contagious, but now we know that social networks play a significant role in weight loss as well,” said lead author Tricia Leahey, of the Miriam Hospital in the U.S.

A study in the Lancet journal earlier this year found that people who joined a diet class such as Weight Watchers lost more than twice as much weight as those who received weight-loss advice from a doctor or nurse.

British Nutrition Foundation identified more than 100 different factors that influence our weight

15. Saying “I can’t” when you’re offered food. Research suggests if you say this when asked if you’d like a slice of cake, you’re less likely to stick to your diet than if you say, “I don’t . . .”

Dr. Vanessa Patrick, of the University of Buffalo, who led the study, says: “Saying <<I can’t>> to temptation inherently signals deprivation and loss. Using the <<I don’t>> strategy shows a sense of determination and empowerment.”

16. Avoiding the mirror. Eating near a mirror can have a powerful effect on how many calories you consume. “One U.S. study showed that eating in front of mirrors slashed the amount people ate by nearly one-third,” says exercise psychologist Dearbhla McCullough, of Roehampton University. “The theory is, having to look yourself in the eye as you eat reminds you of why you’re trying to lose weight.”

17. Being a loner. The more social interaction you have, the more weight you could lose. At least that was what researchers at Ohio State University found when they studied laboratory mice.

Mice forced to socialize led to vast increases in the amount of calorie-burning brown fat compared with ordinary white fat. The researchers put this down to the fact that the mice were more inclined to be active in the groups than alone.

18. Eating dinner off your lap in front of the TV. A study at the University of Birmingham in Alabama found people who were distracted while eating a meal consumed more high-fat snack food afterwards and didn’t even remember what they had eaten.

19. Being stressed. Stress encourages the body to lay on weight around your middle. This is because it triggers the release of a hormone called cortisol. Over time, raised cortisol levels cause belly fat to accumulate and also makes individual fat cells enlarge.

20. Buying too great a variety of foods. Fewer food choices and instilling culinary boredom could be the key to successful weight loss. Researchers reporting in the American Journal of Clinical Nutrition found that when women were offered the same food over and over again, they tended to eat less overall.

21. You’re recently divorced – or just married. Divorce and getting married are kinds of “marital transition that act as weight shocks”, causing us to pile on the pounds, a study of 10,071 people found.

Professor Dmitry Tumin, from Ohio University, found the likelihood of major weight gain after marriage or divorce increased most for people past the age of 30, partly down to comfort eating through stress and anxiety.

22. Playing music while eating. Researchers at Georgia State University showed this could cause you to eat more. If you listen to pop as you chew, make sure the music is slow: a study in the Journal of Applied Social Psychology showed that listening to faster music led people to eat more quickly, while the opposite was true for slower music.

Workouts that don’t work

23. Doing only yoga. It burns just 144 calories in 50 minutes, which is no better than a slow walk. Even a power yoga class burns only 237 calories (half the amount of a circuit class), boosting heart rate to just 62% of its maximum.

“It provides only a mild workout for the heart and lungs (a good workout would be 70-90%),” says John Brewer, professor of sport at the University of Bedfordshire.

24. Exercising alone. You are more likely to give up or not work out as hard. Group exercise unleashes a flood of feel-good chemicals in the brain that could help you stick with physical activity rather than throw in the towel, found a recent study by Oxford University’s Institute of Cognitive and Evolutionary Anthropology.

The researchers also measured pain thresholds and found the group exercisers tolerated hard work much better than those going it alone.

“Making a commitment to meet others also means you are more likely to stick with workouts,” adds Dearbhla McCullough.

25. Lifting heavy weights. Lifting light weights (of 3-5 lb) for more repetitions is just as effective at building muscle as lifting heavy weights, say researchers at McMaster University in Canada.

But while light weights will help you shed fat, lifting heavy weights can cause you to bulk up.

26. Exercising for hours at a steady pace. Short sharp bursts are just as effective and less time-consuming, and you’re more likely to stick at it. Canadian researchers compared the effects of cycling at a moderate pace for 90-120 minutes with a workout of 20-30 seconds of gut-busting pedaling followed by four minutes rest and repeated four to six times.

After two weeks, both groups had almost identical improvements in fitness despite the fact some had only worked out for six to nine minutes a week, but others had put in five hours.

27. Giving in to hunger after exercise. When women exercised hard they ate almost enough calories afterwards to make up for the ones they’d burned, according to a study published in the American Journal of Clinical Nutrition.

28. Doing the wrong type of exercise. Some people, regardless of weight, are programmed not to respond at all to aerobic exercise, says a study led by Jamie Timmons, professor of ageing biology at the University of Birmingham.

It makes no difference to their fitness or insulin sensitivity, the efficiency with which their bodies dealt with blood sugar and a risk factor for diabetes. Jamie Timmons says “endless hours spent jogging, swimming or going to the gym could be a waste of time for up to one-fifth of the population”.

Instead, they should do high intensity, shorter duration exercise such as circuits or weight training.

29. Exercising inside. Most studies show that, compared with exercising indoors, exercising in natural environments is associated with greater boosts to mood, decreased anxiety and an increased likelihood of sticking with the workouts.

30. Doing the wrong exercise for your age. From around our 30s, we lose on average one-fifth of a pound of muscle a year, thanks to a process known as sarcopenia.

“Resistance training in particular – such as lifting weights or kettlebells – becomes as, if not more, important than aerobic workouts as you get older to offset these losses,” says Louise Sutton, head of the Carnegie Centre for Sports Performance at Leeds Metropolitan University.

Why do you need the muscle? It’s vital for burning off fat.

31. Doing only aerobic or weight training. To get fit, you need to mix exercise such as cycling and running, with weight training or resistance work, including some forms of Pilates, according to a recent study in the journal Medicine and Science in Sports and Exercise.

32. Exercising without music. Music is a key motivator, suggest various studies from Brunel University in Middlesex. This is because it both distracts attention from pain as well as simultaneously prompting us to work harder for longer.

“Music is like a legal drug for sporty types,” says Dr. Costas Karageorgis, who led the study.

“It can reduce the perception of effort significantly and increase endurance by as much as 15%.”

It’s all your body’s fault.

33. You don’t have enough brown fat – thin people are known to have higher amounts of beneficial brown fat than the overweight. Brown fat’s great appeal is that it burns calories faster, like a furnace.

A recent study in the Journal of Clinical Investigation found that a form of brown fat is turned on when people get cold.

34. You’re too sensitive to smell. Overweight people gain pounds because they are more sensitive to the smell of food than thinner people, according to a study published in the journal Chemical Senses.

35. Your genes make you hungry. Many genes have been linked to obesity, including brain-derived neurotrophic factor gene, which has been shown to play a role in putting on weight.

Earlier this year, researchers revealed a mutation in this gene seems to disrupt the brain’s response to appetite hormones which leads the body’s message to “stop eating” being blocked.

36. You’re a woman. Using brain scans, U.S. researchers have found overweight men could suppress cravings or what they called “the conscious desire to eat’ more successfully than women. It’s thought hormone differences were involved.

37. Your brain chemicals are out of kilter. The hormone leptin helps control appetite but U.S. researchers found overweight and obese people don’t lack leptin, but their brain isn’t very sensitive to it.

38. It’s your age. “Basal metabolic rate, which accounts for about 50 to 70% of your total energy expenditure, is thought to decrease about 1 to 2% per decade,” says Louise Sutton. After 20, daily energy expenditure decreases about 150 calories per decade. “The upshot is that you need to eat less as you get older,” says Louise Sutton.

39. You’re hard-wired to yo-yo. Scientists now think that soon after fat people lost weight, their metabolism slows and they experience hormonal changes that increase their appetites again.

Last year, a team of Australian researchers reported these effects can be long term.

People “who have lost weight need to remain vigilant and understand that once they have lost weight the battle is not over,” says Joseph Proietto, the professor of medicine who led the study.

40. Your parents made you fat: whether you are fat or thin could be an inherited factor. A 2009 UK study showed only four per cent of girls with normal-weight mothers were obese, compared with 41% with fat mothers.

Research in the International Journal of Obesity suggests a very strong link between mother and daughter and father and son obesity, but no link across the gender divide.