Can't lose weight? A new book argues that it's all those toxins that upset your body's weight-control systems

Another week, another weight-loss book. Every dieter worth their Slim-Fast will have read their share of slimmers "bibles", in which they place their faith, religiously following one punishing diet after another, hoping that they will shed the old pounds and shape a new body. But, time and time again, the battle against the bulge is lost. Statistics show that 45% of men and 34% of women in the UK are overweight and a further 10% of men and 18% of women are obese, despite our apparently insatiable appetite for food fads, detox diets and exotic exercise regimes. Even when we do succeed in shifting the weight, once we finally forgo the diet to resume a normal eating regime, the pounds creep back on – usually with interest. Our efforts are frustrating and our suffering apparently futile, as that slim, svelte body continues to elude us.

According to Dr Paula Baillie-Hamilton (who is a medical doctor with a PhD in human metabolism), there is another culprit for making us fat, aside from one too many pies. Dr Baillie-Hamilton reckons we should stop just counting energy calories and start counting "chemical calories". She believes the presence of toxic chemicals in our food and environment is destroying our body's natural ability to control our weight, damaging our appetite, metabolism and hormone levels – what she collectively refers to as our slimming system.

In her new book, The Detox Diet: eliminate chemical calories and restore your body's natural slimming system, Dr Baillie-Hamilton explains her conviction that the toxins and synthetic chemicals that are used on our livestock and crops are making us fat. Revolutionary and radical though it may seem, there is rationale behind her theory. Steroids, antibiotics and a toxic cocktail of other synthetic chemicals are pumped into animals to increase their body fat by damaging their metabolism and weight-control hormones. While there are only traces of such toxins in the food we eat, if you translate the damage done to the "slimming systems" of livestock to our own bodies, it doesn't bode well for our weight-watching plans.

What's more, Baillie-Hamilton has a shock in store for those sadistic slimmers who have been passing on the bread and butter for years in favour of the green/side/fruit salad. It would seem that the fruit and vegetables that are prone to damage, or those that are more perishable, such as lettuce and celery, contain some of the highest traces of toxins. Some apples, for example, have been treated with as many as 21 different pesticides – so perhaps it's time to rethink what's in the lunchbox.

The good news, according to Dr Baillie-Hamilton, is that if we give those foods with high traces of toxins a wide berth and replace as much of our food as possible with the organic alternative, then our slimming system will soon be restored and a stable, healthy, weight regained. Flagging up the "dirty dozen" – 12 foods that she claims contain the highest traces of toxins and synthetic chemicals – Baillie-Hamilton exposes enough food offenders to make every health conscious shopper think twice about what's on their list. Lamb, Salmon, trout, oranges and lettuce have all been black-marked while apples, apricots, strawberries and potatoes are a just a few of the other malefactors that linger just outside the top 12. Could Dr Baillie-Hamilton be right? Could the chemicals present in those foods that have been the mainstay of a healthy British diet for years be the reason why some people just can't lose weight?

Dr Colette Kelly of the British Nutrition Foundation firmly disagrees and believes we should take stock of the scientific facts before making a pariah of the potato. "There is no medical evidence to suggest that what Dr Baillie-Hamilton claims is true," she says. "People gain weight if their calorific intake exceeds their energy output – it's as straightforward as that. Pesticides and hormones that are used on crops and livestock cannot be blamed for weight gain. Their levels are regulated and rigorously controlled and the levels at which they are present in our food is not enough to do the damage she suggests." Dr Kelly is also angered by the contradictory message that Dr Baillie-Hamilton's book sends out. "We have been trying to encourage people to include more oily fish, fruit and vegetables in their diet as they have no end of health benefits. Dr Baillie-Hamilton is confusing the consumer with her new book – sending out the signal that these foods are bad for us."

What Dr Kelly says is hardly news. Fish, fruit and vegetables are the staples of every healthy diet and should not be slung out of the trolley in a fit of food paranoia. However, while the conclusions that Dr Baillie-Hamilton have reached may seem extreme, it is hard not to be disconcerted by the sobering connections she has made between toxins and our health. Perhaps the argument that they are responsible for damaging our slimming system is tenuous, but eating an average of 21 different chemicals every time you have an apple can't be a good thing. The detriment to our health may be slow in showing or difficult in proving, but going organic seems like an increasingly good idea.