Brace yourself if you are one of the many women constantly struggling to lose weight. You may want to hurl your alfalfa-sprout salad at me for daring to mention this, but there are women — albeit a minority — who are underweight and unhappy about it. Strangely, it is socially acceptable to call them skinny cows to their face, even though calling someone fat would have people seriously questioning your manners. Even Jade Goody might have had some supporters if anyone had bullied her with taunts of “yer fat cow”.

It may seem incredible to those of us who have ever fought excess weight, but many thin women are actually unhappy about being underweight. They suffer largely in silence, because the majority of us are so desperate to be skinny that we readily mock those rare women who are naturally so. Thinness may be generally desirable in our society, but thin women can be distressed when others cast aspersions on their mental and physical health. Researchers have found that although underweight bodies are perceived as more attractive than overweight ones, they are also considered to belong to less emotionally stable women. Let me be clear here — I am talking about women who are thin naturally, not women who are masking any degree of anorexia or any other tormenting state in which weight is obsessively and secretively controlled.

Some slight women are also just as anxious about their health. “I know eating all that chocolate and all those fry-ups is terrible for me,” one confided. “But because I know I can get away with it figure-wise, I ignore the fact that it’s bad news for my long-term health.” Real skinnies can and should take steps to change their life. If that sounds like you, there are three main courses of action to consider: accepting your genetic make-up; getting medical checks for conditions that can cause or perpetuate being underweight; and altering your diet and exercise regime to fatten you up.

The first one aside, lifestyle and/or biochemical imbalances may be keeping you thin. If you are genetically inclined to slimness, you will struggle to keep weight on if you smoke, are highly strung or exercise madly. Similarly, along with other symptoms (from constant fatigue to bloating), unexplained weight loss or difficulty in keeping weight on can be a sign of an overactive thyroid, diabetes, poor absorption of nutrients, digestive disorders and other conditions, so it is worth checking with your doctor and a nutritionist. To find a good nutritionist, ask your GP for a referral or visit the website of the British Association for Nutritional Therapy, at www.bant.org.uk.

If you are told that your thyroid is overactive, try to eat more of foods that contain goitrogens, which naturally suppress thyroid function. They include soya and cruciferous vegetables such as broccoli, cauliflower, sprouts, cabbage and kale. If poor absorption is diagnosed by your doctor, you need foods that will soothe the gut. Simply cramming in sugary, fatty junk foods to increase weight will irritate it. And, obvious though it sounds, you need to eat three full meals a day, plus substantial snacks in between if your appetite is small.

As for the fry-ups and chocolate, they may come back and bite you on your (albeit tiny) bottom. Being underweight does not render you immune to heart disease, diabetes, rapid ageing and serious illness. So you need to take as much care as everyone else to get the most from your diet. It is unwise to bulk up on so-called fattening foods or those with a high glycaemic index. A diet of pastries and pork pies will just leave you bloated and lacking energy, and it will increase your risk of cardiovascular disease and of diabetes.

The ideal is to gain just a couple of pounds (1kg) a month (any more is unlikely to stick), for which you will need to eat about 300 extra calories a day. Nutritious, calorie-dense foods are best, especially those containing healthy fats, such as nuts, seeds, avocados and their oils. For example, just adding 2 tbsp of flaxseed oil to cereal, yoghurt, a smoothie or vegetables notches up 240 calories. That is well over 10% of a woman’s typical daily requirement.

I was the resident nutritionist on a fitness holiday where I had to give one thin guest extra sandwiches of peanut butter on rye bread to prevent her from losing weight. (Two slices with a scraping of butter and peanut butter provide about 300 calories.) As a celebrity stylist, she was used to being around dozens of “fake skinnies”, and she was becoming increasingly upset by people’s attitudes toward her. “I’m sick of people thinking I’m screwed up about food,” she said, exasperated.

The trick to gaining weight healthily is to add in a little more food here and there, rather than stuffing yourself with empty calories in a bid for extra curves. At breakfast time, help yourself to an extra spoonful of cereal or slice of toast; drizzle a little more olive oil on your salad at lunch; and have a second helping of rice at supper. A few desserts a week are fine, but avoid eating a mass of sugar and white flour daily. Do not count calories obsessively; instead, choose substantial, healthy meals, keeping the creamy, fried and sugary options to a minimum.

Any sports trainer will tell you that the best way to gain weight is to concentrate on weight training, as opposed to cardiovascular exercise. That does not have to mean pumping iron and bulking up. It’s more about transforming a weedy, scrawny body into a strong, lean and well-toned one. I would always recommend getting the advice of an expert trainer to start you off. That way, you can be precise about your goals and have the right programme to achieve them.

I have to admit (and this is likely to further dieters’ jealousy) that it is not easy for a skinny minnie to gain weight, even with all those strategies. So, any of you who are fed up with sarcastic insinuations about your body and relationship with food could either accept your lot or try the opposite strategy. Blithely insulting your larger friends would probably shut them up and give them something to chew on.

What a skinny cow probably eats

Breakfast: Pain au raisin and blueberry muffin OR a full fry-up; double-shot latte

Lunch: BLT and crisps; diet coke

Supper: Readymeal moussaka; glass of wine

Snacks: Crisps; chocolate; muffins; biscuits

What a skinny cow should eat

Breakfast: Nutty muesli and fruit yoghurt; smoothie OR grilled bacon, poached eggs, grilled tomatoes and wholegrain toast; regular cappuccino

Lunch: Chicken or hummus and avocado wholegrain sandwich with lentil or tomato soup; apple juice

Supper: Ready-to-cook steak or salmon with rice and broccoli, drizzled with oil; glass of wine

Snacks: Wholegrain toast or crackers with peanut butter or hummus, muesli bars, raw nuts, yoghurt, fruit scones

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