Top 10 diet myths
Written by Elizabeth Openshaw, health journalist
Need to lose weight? Before you give up the late night munching and go on a no-fat detox frenzy to kick your sluggish metabolism into shape, read what the experts have to say about these popular dieting myths.
Myth 1
Myth
Low-fat or no-fat diets are good for you.
A low-fat diet can help weight loss, but don't cut out fat altogether.
Fact
Leading dietician Lyndel Costain says: 'People tend to think they need a low-fat diet to lose weight, but you should still have a third of your calories coming from fat.'
The body needs fat for energy, tissue repair and to transport vitamins A, D, E and K around the body.
Lyndel Costain adds: 'As a guideline, women need 70g of fat a day (95g for men) with 30g as the minimum (40g for men).
'There's no need to follow a fat-free diet. Cutting down on saturated fats and eating unsaturated fats, found in things like olive oil and avocados, will help.'
Myth 2
Myth
Crash dieting or fasting makes you lose weight.
Fact
This may be true in the short term, but ultimately it can hinder weight loss.
Claire MacEvilly, a nutritionist at the MRC Human Nutrition Research Centre in Cambridge, explains: 'Losing weight over the long term burns off fat. Crash dieting or fasting not only removes fat but also lean muscle and tissue.'
The loss of lean muscle causes a fall in your basal metabolic rate - the amount of calories your body needs on a daily basis.
This means your body will need fewer calories than it did previously, making weight gain more likely once you stop dieting.
It's also why exercise is recommended in any weight-loss plan to build muscle and maintain your metabolic rate.
Claire MacEvilly adds: 'Fasting can also make you feel dizzy or weak so it's much better to try long-term weight loss.'
Myth 3
Myth
Food eaten late at night is more fattening.
Fact
Many diets tell you not to eat after a certain time in the evening. They say the body will store more fat because it is not burned off with any activity.
A study at the Dunn Nutrition Centre in Cambridge suggests otherwise.
Volunteers were placed in a whole body calorimeter, which measures calories burned and stored.
They were fed with a large lunch and small evening meal for one test period, then a small lunch and large evening meal during a second test period.
The results revealed the large meal eaten late at night did not make the body store more fat.
It's not when you eat that's important, but the total amount you consume in a 24-hour period.
Lyndel Costain adds: 'It is true that people who skip meals during the day, then eat loads in the evening are more likely to be overweight than those who eat regularly throughout the day.
'This may be because eating regular meals helps people regulate their appetite and overall food intake.'
Myth 4
Myth
A slow metabolism prevents weight loss.
Fact
This is a common myth among dieters who are struggling to lose weight.
Studies have shown that resting metabolism - the number of calories used by the body at rest - increases as people become fatter.
In other words, the larger you are, the more calories you need to keep your body going and the higher your metabolism.
Clare Grace, research dietitian at the Queen Mary University of London, says: 'Weight gain occurs when the number of calories eaten is greater than the number used up by the body.
'Unfortunately, people are becoming increasingly sedentary, burning off less and less calories, and it seems likely this is a crucial factor in the increasing numbers struggling to control their weight.'
Myth 5
Myth
Fattening foods equal rapid weight gain.
Fact
Believe it or not, true weight gain is a slow process. You need to eat an extra 3500 calories to gain one pound of body fat (and vice versa for losing it).
Lyndel Costain explains: 'If the scales say you've gained a few pounds after a meal out, it's largely due to fluid, which will resolve itself - as long as you don't get fed up, and keep overeating!
'A lot of people feel guilty and think they've blown their diet if they eat rich foods. But, how can a 50g chocolate bar make you instantly put on pounds?
'For long-term weight control, balance high-fat foods with healthy food and activity.'
Myth 6
Myth
Low-fat milk has less calcium than full-fat milk.
Fact
Skimmed and semi-skimmed milk actually have more calcium, says dietician Alison Sullivan, because the calcium is in the watery part, not the creamy part.
She says: 'If you're trying to lose weight and cut fat from your diet, skimmed milk is your best bet because it is lower in fat and has 10mg more calcium per 200ml milk than full fat.
'Semi-skimmed is best for maintaining a healthy lifestyle if you're not dieting.
'Full-fat milk is best for children and adults who are underweight.'
Myth 7
Myth
Low-fat foods help you lose weight.
Fact
'Low-fat' or 'fat-free' doesn't necessarily mean low calorie or calorie-free, warns Lyndel Costain.
Check the calorie content of foods, especially cakes, biscuits, crisps, ice creams and ready meals.
Extra sugars and thickeners are often added to boost flavour and texture, so calorie content may be only a bit less, or similar to standard products.
Foods labelled low-fat should contain no more than 3g fat per 100g.
'Watching the quantity is important,' adds nutritionist Alison Sullivan. 'People tend to have half-fat spread but then use twice as much.
'And things like fruit pastilles may be low in fat, but are high in sugar which turns to fat.
'With low fat foods, look to see where else the calories might come from.'
Myth 8
Myth
Cholesterol is bad for you.
Fact
Cholesterol is a fatty substance that is made mostly by the liver.
It can be bad for us, because it forms deposits that line and clog our arteries. Clogged arteries contribute to heart disease.
But we all need some blood cholesterol because it's used to build cells and make vital hormones - and there's good and bad cholesterol.
Lyndel Costain explains: 'Saturated fats found in food like meat, cheese, cream, butter and processed pastries tend to raise low density lipoprotein (LDL) cholesterol, known as 'bad' cholesterol, which delivers cholesterol to the arteries.
'High density lipoprotein (HDL), or 'good' cholesterol, transports cholesterol away from the arteries, back to the liver.'
So choose unsaturated fats such as vegetable oils, nuts and seeds.
Myth 9
Banana myth
Many people believe bananas are fattening.
Bananas are low in fat and are packed with potassium.
There is only 0.5g fat and 95 calories in a banana.
Myth
Vegetarians can't build muscle.
Fact
Vegetarians can be as muscular as meat eaters by getting their protein from vegetable sources such as cheese, nuts, pulses and grains.
Claire MacEvilly says: 'You need protein to build muscle, but too much can lead to long-term side effects.
'The body can only store a certain amount of protein, so too much can damage the kidney.
'The Department of Health recommends that 50 per cent of energy should come from carbohydrates, 35 per cent from fat and the remaining 15 per cent from protein.'
Myth 10
Myth
You always gain weight when you stop smoking.
Fact
Some people gain weight when they stop smoking, some lose weight and some stay the same.
While nicotine does increase the body's metabolism, its effect is small. It's far healthier to be an overweight non-smoker than not bother giving up because you think you'll put on weight.
Alison Sullivan says: 'Where people tend to fall down is when they replace a cigarette with comfort food.
'Chewing sugar-free gum or snacking on vegetable strips kept in the fridge is a good idea because you can have these instead of reaching for the biscuit tin.
'And something like a satsuma keeps your hands occupied until the craving goes away.'
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