So what do slim women really eat?

Studies show that, from young adulthood, we gain a pound a year, and become more apple shaped. Our metabolic rate also falls, making it harder to stay trim. But some women can still slip into the same size clothes as in their teens. What's their secret?

‘I'm the same weight I was at 12'

Carrie Saint, a writer, 48, from Leamington Spa, Warwickshire, is 5ft 2in and weighs 71⁄2st

‘It's rare that I get on the scales, but I know I'm the same weight now as when I started secondary school. I put on a stone when I was unhappy at university, but overeating and the wrong foods make me uncomfortable and out of sorts. I simply don't crave fatty, fried or sweet foods at all.

'My preference for healthy food stems from having constipation as a child and working out that a high-fibre diet, with lots of fruit and vegetable, was the only way to feel comfortable. I invented interesting salads with courgettes, raw mushrooms (which seemed exotic then!) and baked beans, as well as chopped white cabbage, grated carrots, peppers and beansprouts. I made dressings with natural yoghurt, a dash of vinegar and salad cream, a bit of curry powder or tomato ketchup, plus herbs and ground black pepper. When I was pregnant with my twins, Alex and Benjy, my eating habits didn't change, so I had no baby weight to lose. These days, I still eat mostly vegetable matter.

'My partner Richard and I always sit down with the boys to eat. At 15, they are both vegetarians, but Richard and I eat fish and some meat. I always eat breakfast and, because I work from home, I can use my pressure cooker to make quick homemade soups for lunch. Or I'll have a boiled egg and buttered soldiers. My main meal of the day is in the evening, never earlier than 8pm. I might have a small bowl of cereal, some yoghurt and fruit or cottage cheese to keep me going during the afternoon, but don't do much other snacking, apart from fruit. Occasionally, I'll crave a bit of chocolate, but a fun-sized bar usually does the trick. My weakness is wine - I have a couple of glasses most evenings.

'Running helps keep me slim - I do around half an hour at least three times a week and, if I don't, I feel sluggish and my energy levels dip. I do a gym workout once a week, too.'

Carrie's daily diet

Breakfast Slice of wholemeal toast (from breadmaker) with jam and Greek yoghurt, 250 cals. Instant milky coffee, 20 cals

Lunch Bowl of homemade lentil soup, a tablespoon of Greek yoghurt and sprinkle of Parmesan with a slice of buttered wholemeal bread, 422 cal. Low-sugar orange squash, 2 cals

Dinner Couscous with several different vegetables, small, grilled salmon steak with mustard, lime juice and honey, 612 cals. Satsuma and finger of cheddar, 128 cals. 2-3 glasses of wine, 346 cals

Total: 1,780 calories

‘I love my sweet treats'

Alison Miles, 50, a PR consultant, lives in London. She is 5ft 6in and has weighed between 8st 3lb and 8st 7lb all her adult life

‘As a child, we ate wholesome, home-cooked food. My parents said our bodies were like a boiler - if you put good stuff in, you got good work out. I went back to my pre-pregnancy size after my children, and my metabolism isn't slowing yet - I can still eat treats without immediately wearing them. Maybe it's because I'm always on the go. For breakfast, I have fruit juice and cereal with milk, plus a slice of toast.

'I'm far from virtuous though - I love my cakes. If I'm going from meeting to meeting, I'll grab a pastry mid-morning. Lunch could be anything from a sandwich to a business lunch. But I often work from home and can forget to eat when I'm stressed. When my son Edward, 16, comes in from school, we'll have a cuppa and a scone, or snack on dips or olives. For dinner, we'll have pasta, sausages, chicken, baked potatoes or a curry. We sometimes have a takeaway on a Friday and there are always pizzas in the freezer. But I never pile my plate too high, as I find it off-putting.

'I often have pudding - I'd find it really hard to be on a diet that meant I had to deny myself sweet stuff. But I wouldn't sit down and eat a whole bar of chocolate - that just doesn't appeal. Fitting exercise in with work is hard, but I walk as much as I can and don't use the car unless I have to.'

Alison's daily diet

Breakfast 2 Weetabix and milk, 189 cals. Cup of tea with milk, 15 cals. Glass of orange juice, 72 cals.

Lunch Homemade mozzarella, avocado and tomato salad with two slices of organic white bread and a banana, 611 cals. Glass of tap water, 0 cals

Afternoon Cup of tea, 15 cals. Chocolate mini roll, 120 cals

Dinner Olives, 24 calories. Chicken breast wrapped in bacon with onion, garlic and roasted veg, with potatoes or pasta, and broccoli, 509 cals. Individual clotted cream rice pudding, 335 cals. Glass of tap water, 0 cals

Evening snack Apple, 47 cals

Total: 1,937 calories

What's their secret?

Nutritionist Angela Dowden says: ‘Women like Alison take in just the right amount of calories to keep them from gaining or losing weight. They've found a long-term way of eating, which keeps their weight stable. They tend to eat bulkier foods such as fruits and veg, that fill them up, but not out. There is also no need to have hang-ups about eating ‘naughty' foods in moderation.

'They may have a genetic predisposition towards a smaller appetite, but, on the whole, it is about their mindset and lifestyle, not some lucky gene.'

Photos: Sam Jones