London - Everyone who has ever tried to lose weight knows the formula: eat less and move more. According to this, what you eat doesn’t matter so much, as long as you keep an eye on the total number of calories - though it’s best to avoid fat because not only has it got more calories, but one type of fat, the saturated kind, raises your risk of heart disease, too.
This has been the thinking behind the low-fat, high-carbohydrate diet that has been the cornerstone of dieting and healthy eating for more than 40 years.
But today, this mantra is increasingly being questioned by clinicians and nutritional scientists - not least because it seems to have failed to halt the obesity epidemic.
The sceptics believe that the idea of all calories being equal is flawed.
Indeed, Professor David Lawrence, an expert in nutrition and obesity data analysis, said recently in the journal BMC Medicine that the idea is based ‘on an outdated understanding of the science’.
The sceptics argue that calories from different sources have different effects on the body, with calories from carbohydrates more likely to encourage weight gain.
Not only is the calorie theory under attack, but evidence is also emerging to show that lowering fat might not cut heart-disease risk, after all.
A major study published in the authoritative New England Journal of Medicine compared the clinical benefits of a conventional low-fat diet with two types of Mediterranean diet, which are naturally considerably higher in fat.
The study had to be stopped early because the heart attack and stroke rate in the Mediterranean options was so much lower it was deemed irresponsible to keep patients on the conventional diet.
WILL CREAM AND BACON HELP YOU LOSE WEIGHT?
Faced with mounting evidence, Swedish dietary experts recently made a dramatic U-turn, recommending a low-carb, rather than low-fat, diet for weight loss.
The bombshell came from the Council on Health Technology Assessment, which advises the Swedish government. Based on a review of 16,000 studies, it said the best sorts of food for losing weight were the likes of olive oil, double cream and bacon.
So the rules are being rewritten: to lose weight, cut down on carbs and eat more fat.
So what, precisely, is behind this new thinking? It comes down to the effect different foods have on your hormones.
The most important of these hormones, and the one that’s crucial for weight loss, is insulin.
Insulin is the hormone that controls fat storage. A high-carb diet increases the amount of glucose in the bloodstream, which in turn means you produce more insulin. The more insulin the body produces, the more fat gets stored. A low-carb diet means less insulin, making it easier to lose weight because less fat is then stored.
MORE CALORIES, BUT SLIMMER WAIST
Dramatic new support for this has come from a unique experiment conducted by a personal trainer from East London.
As Sam Feltham explains: ‘My business is helping people to lose weight, and if all calories aren’t equal, that could make a real difference.’
A few months ago, Sam upped his intake to a massive 5,000 calories every day. For three weeks he got these calories from a low-fat, high-carb diet; for another three, he ate more fat and cut right back on carbs.
He did exactly the same, moderate exercise regimen each time.
Now, according to the conventional wisdom, the weight gain would be the same on both regimens. After all, a calorie is just a calorie.
In fact, on the low-fat diet Sam stacked on 16 lb (7.2kg) and gained 9.5 cm around his middle.
But when he ate more fat and cut his carbs, he added just 2½ lb (1.1kg) and lost 2.5cm from his waistline.
‘I’ve long been sceptical of the claim that all calories are created equal,’ says Sam, who’s just over 6 ft tall and normally weighs 14 st (89 kg).
‘I’m sure I eat more calories than I burn, yet my weight and waist measurement normally remain the same.’
Sam, who survived childhood cancer (Hodgkin’s lymphoma), wondered if his usual low-carb diet was the key, and set about his experiment to find out.
For the low-carb, high-fat part of the experiment, Sam got his 5,000 calories from foods such as eggs, mackerel (which is very fatty), steak, green veg and coconut oil, interspersed with three snacks of nuts - walnuts, pecans or almonds (which are naturally high in fat).
While 72 percent of his total calorie intake came from fats, 22 percent came from protein and just 5.9 percent from carbs. Each meal was exactly the same every day.
With the high-carb diet, most of his calories (63 percent) came from carbohydrates, 13 percent from protein, and 22 percent from fat.
He ate garlic bread, low-fat lasagne, crumpets, low-fat yoghurts and rice pudding, chocolate muffins and wholemeal bread.
Admittedly the types of fat on his high-fat diet weren’t your usual fatty foods, such as cream and butter. And his high-carb diet wasn’t exactly ‘healthy’.
But the point was not comparing the health benefits of the two, says Sam. ‘It was an experiment to test the idea that different foods affect your body’s biochemistry differently.
‘If it is true that cutting calories is the key to weight loss, then excess calories should put on the same amount of weight whether they come from a “healthy” diet full of fat or a poor diet full of carbs.’
He says he was ‘really surprised’ at how little weight he put on with the low-carb/high-fat diet, while on the high-carb/low-fat diet his body fat increased from 12.7 percent of his body weight to 16.9 percent.
CARBS MAY RAISE CHOLESTEROL
While Sam’s experiment was by no means a scientific one, as well as the weight gain, what was even more striking was what an unhealthy effect the high carbohydrate regimen had on standard markers for heart health.
For when Sam had his blood tested after his three weeks on high carbs, ‘the diet effectively gave him metabolic syndrome’, says Dr Aseem Malhotra, a cardiologist at the Royal Free Hospital in London (who speaks with the added authority of having recently co-authored a report on tackling obesity for the Academy of Medical Royal Colleges).
Metabolic syndrome is a precursor to heart disease and diabetes.
‘Particularly worrying was that his triglycerides (fats in his blood) had gone up four times, while his so-called ‘good’ (HDL) cholesterol had dropped,’ says Dr Malhotra.
‘That is not a good combination. Add to that the increase in his waist measurement, and he was looking a lot less healthy than he had been.
‘What’s more, a level of inflammation in his liver had doubled, which is also linked with diabetes and heart disease.
‘If someone came into my clinic in that state, I’d make it clear they needed to make some serious changes to their diet and start eating a diet low in carbs. I was really surprised that the damaging changes had happened so quickly.’
Did the fact that, as a personal trainer, Sam was obviously very fit at the start of his trial make a difference?
‘Absolutely,’ says Dr Malhotra. ‘It is alarming to think that if a high-carb diet can have that effect on him in three weeks, what is it doing to people who don’t exercise and eat like that for years?’
IS STANDARD DIET ADVICE WRONG?
‘This is a vivid illustration of the fact that the conventional idea of what causes weight gain is back to front,’ says Dr Malhotra. ‘We’ve been told for years that eating fat will make you fat because it contains twice the calories that are in carbohydrates. That is to misunderstand how fat storage works.
‘Research has already shown that if you are eating a high-carb diet, and so have high levels of insulin, you are likely to have more fat in your blood than someone on a high- fat diet.
‘This is what happened to Sam.’
WON'T FAT CLOG UP ARTERIES?
But doesn’t eating extra fat clog up your arteries? No, insists Dr Malhotra. In fact, he says, it’s too many carbs that are the problem.
He argues that - as seen with Sam - a high-carb diet tends to lower the good HDL cholesterol that helps keep arteries clear.
At the same time, as glucose from carbs is turned into fat for storage in the body, fatty acids are also produced.
It is this combination of fatty acids and low HDL, not saturated fat, that ‘clogs your arteries,’ says Dr Malhotra.
Recent research supports the idea that warning about saturated fat in the diet has probably been a mistake.
‘The influence of dietary fats on serum cholesterol has been overstated,’ say the authors of a review in Advances In Nutrition in May. ‘The lack of any clear evidence that high-fat foods lead to adverse health effects makes one wonder how they got such a bad name.’
Demonising fat and encouraging people to eat more carbs can be harmful to people with heart disease, says Dr Malhotra. ‘I see patients who have had a heart attack and are trying to lose weight on a low-fat diet and are puzzled because they are gaining weight.
‘When I investigate, it is usually because they are eating lots of low-fat supermarket foods which are also high in carbs such as sugar.
‘When I get them eating real foods and not worrying about fat, their weight starts to come down.’
But what about other side-effects? After all, Sam’s high-fat diet has close parallels with the Atkins diet - a low-carb diet which has been linked with side-effects ranging from bad breath and constipation to more serious problems including a lack of bone-building calcium and kidney problems.
But the evidence for these side-effects is mixed. Furthermore, those eating low-carb these days are much more flexible about the amount of fat they get. Research is still needed to sort out the best ratio of carbs to fat.
NO CHANGE TO OFFICIAL ADVICE
So will UK dietary experts soon be recommending a Swedish style U-turn in healthy eating advice?
Not according to British Dietetic Association spokesperson Chris Cashin. She says Sam gained weight ‘more slowly on the high-fat diet - but if he had continued with them for longer, I suspect the two diets would have ended up producing the same amount of weight gain.
‘That is what we have seen in other studies.’
She also considered his high-fat diet very unhealthy.
‘I’ve had clients who have tried these diets and they can have dreadful problems because of all the extra fat and the large amount of fibre from the nuts. They have terrible diarrhoea.’ (Sam says he experienced no such problems.)
Chris Cashin also questions if he got the amount of calories he claims, and points out that the experiment wasn’t at all scientific.
For his part, Dr Malhotra is keen for the results of Sam’s experiment to be put on a firmer scientific footing because they could be highlighting something important.
‘We are spending a fortune trying to cope with metabolic diseases such as diabetes, cancer and obesity. Switching to a low-carb diet would make cutting sugar even more vital and give us a much more effective tool for prevention or treatment.’ - Daily Mail