Demi
Sat, May-06-06, 04:00
The Times
London, UK
6 May, 2006
A Yale University doctor has devised a diet that tricks the brain. Is it science or snake oil, asks Vivienne Parry
It’s not often that a doctor who’s the author of a diet book admits that “it’s a gimmick”. But this is no ordinary diet doc. Come to that, this is no ordinary diet either; it’s based on an intriguing and little-known neurological phenomenon: sensory specific satiety. If you’ve not heard of it before, you certainly will when the Flavour Point diet hits town this month. It’s the brain child of Dr David Katz, a public health doctor from the Yale Prevention Centre in Conneticut.
I’ve never been on a diet; I regard fad diet doctors, particularly American bestselling ones, as creatures beyond contempt and those who drape their money-making activities in a robe of science as the worst sort of charlatans. So Dr Katz, a slight (and skinny) figure, was unknowingly walking into a minefield in agreeing to be interviewed by me.
His diet exploits an evolutionary device hard-wired into human brains. We are programmed to eat more if there is a variety of tastes available and to eat less if only one taste is on offer. It’s a device that drives us to seek alternative food sources, thereby making it more likely that we will get the range of nutrients we need to stay healthy.
This is because the brain is in charge of eating behaviour. The taste of our food registers in the appetite centre of the brain, lodged inside the hypothalamus which, depending on the flavours it receives, sends out signals via hormones to eat more or less. If we are eating just one food, the hypothalamus makes the taste of that food (and tastes similar to it) less pleasant and makes us feel full, thus encouraging us to stop eating and to forage for something different. If confronted with lots of tastes, the human appetite centre remains stimulated and encourages us to eat lots while the food is available.
This is called sensory specific satiety and it is the most important factor controlling how much food we eat at a meal. It’s the reason we can eat a Christmas dinner until we’re stuffed but can still say: “What’s for afters?” Our taste buds may have begun to pall on the savoury turkey and vegetables; our brain makes it taste less pleasant after the second helping. But the prospect of sweet Christmas pudding is very different and our brain allows our appetite to be stimulated once again.
We can graze endlessly at a buffet for the same reason; so many tastes leave our appetite continually restimulated. And modern food production methods are building on the principle of sensory specific satiety to encourage many of us to overeat. Many foods today contain so many ingredients and products that the brain’s appetite centre becomes confused. A savoury snack such as a sausage roll may sound simple but it is bursting with hidden flavours such as sugar and flavour enhancers.
This complexity of taste means that appetite is continually being restimulated — the brain encourages the body to have more and more of it in an attempt to maximise the nutrients seemingly on offer. The very feature designed to protect our health now threatens it.
All this informs the Flavour Point diet. Dr Katz has created a meal plan that revolves around giving people similar flavours throughout the day. So there are onion days, tomato days, sesame days and so on (see box below). Sometimes the similar flavours will be hidden, but they will have an effect on the brain and our appetite all the same. If we follow strictly, we won’t feel hungry. Or so the claim goes.
Dr Katz is is a proper academic, with a fine reputation among his peers and many publications to his name. The Yale Prevention Centre, which concentrates on studying the causes of chronic diseases, particularly diabetes, is funded by the Centres for Disease Control and Prevention and the US National Institute of Medical Health. So far, so good.
Dr Katz says he is appalled at some of the fad diet books (big tick) and was one of the most outspoken critics of the Atkins diet. “It was silly and bad nutrition. Dieting isn’t about weight loss by any means. If it were, we’d just hand cocaine to everyone.” (Cocaine is one of the most potent appetite-suppressants known.) He wanted to find a diet that was good nutrition, that didn’t ignore basic nutritional advice and that people could use easily.
In 1991 he stumbled across sensory specific satiety and was intrigued. “It’s rare that you come across something genuinely novel in medicine, but this was,” he says. The whole principle of sensory specific satiety was discovered only 30 years ago. The pioneer in the field was the American nutritionist Barbara Rolls and her husband Edmund.
In one breakthrough experiment, they gave 24 women test meals, all tasting the same and seemingly being the same, but concealing a wide variety of calories. Some were packed, others were virtually calorie-free. An hour after the meal, all the women were offered cheese and crackers (a different taste from the previous offering) and all of them ate the same amount, regardless of how high their calorie intake had been in the previous meal. Given a new taste, even the brains of those who had consumed most calories were not registering as “full”.
This is a sensory specific satiety effect. In another experiment, 32 people were fed meals that varied in taste and texture. The participants found sweet foods less pleasurable when they had recently eaten sweet foods and salty foods less pleasurable if they had recently had salty ones. It’s fairly obvious, but their research highlighted the effect for science.
Edmund Rolls, now a professor of experimental psychology at Oxford, explains the power of sensory specific satiety. “Even the smell of one food for about the time that you would normally chew it will diminish its pleasantness,” he says. Should any of you become a little overexcited at the prospect of the ultimate “sniff but don’t eat” diet, your body soon twigs that you haven’t actually eaten anything. But it is clear that this effect can be exploited and Dr Katz has done this. The central message of his diet is that by limiting flavours, your body thinks it has had enough long before it would do so if you were taking in many flavours at a time. It cuts out processed foods, which Dr Katz says are engineered to exploit the appetite stimulus that multiple flavours provide. The sort of straw- berry milkshake sold in fast food stores has recently been revealed to contain up to 59 ingredients. If you made it at home, it would contain three or four at most.
“When you taste so many flavours at once, whether from eating too many different foods or too many flavours processed into one food, you overeat before feeling full,” says Dr Katz.
It is the Flavour Point diet’s one-a-day flavour themes that he admits is the gimmick. But the idea of restricting flavours and sticking to simple foods is not. And because of the diet’s reliance on simple food, it has the benefit of sticking to the natural ingredients that are good for you anyway.
All of the recipes based around a day’s theme are calorie-counted. Most come out at about 1,500 calories a day and are low in fat, high in fibre, pay attention to glycaemic load and so on. Anyone would lose weight on such a regimen, so what makes this different? Such a low-calorie diet should also make you feel hungry and the point here is that the 20 guinea pigs Dr Katz used for his diet didn’t feel peckish.
In fact, some of the women in his study complained that they had to eat too much. And they all lost weight at the rate of about 1lb (450g) a week.
So will this diet work in the long term? I was delighted to hear Dr Katz say that he didn’t know. Honesty in a diet doc — hallelujah! But he insisted this wasn’t a fad, that it exploited a genuine phenomenon and it was food that could be eaten by the whole family.
Orange diary: a menu from the Flavour Point diet
BREAKFAST
A small bowl of wholegrain cereal with skimmed milk and a glass of 100 per cent orange juice
MID-MORNING SNACK
A small bowl of fat-free natural yoghurt with a sliced orange
LUNCH
A spinach and orange-lentil salad with feta cheese and pecans
MID-AFTERNOON SNACK
Orange and banana smoothie
DINNER
Orange cod served with green beans with orange peel, bulgar wheat and a tossed garden salad
http://www.timesonline.co.uk/newspaper/0,,175-2165257,00.html
London, UK
6 May, 2006
A Yale University doctor has devised a diet that tricks the brain. Is it science or snake oil, asks Vivienne Parry
It’s not often that a doctor who’s the author of a diet book admits that “it’s a gimmick”. But this is no ordinary diet doc. Come to that, this is no ordinary diet either; it’s based on an intriguing and little-known neurological phenomenon: sensory specific satiety. If you’ve not heard of it before, you certainly will when the Flavour Point diet hits town this month. It’s the brain child of Dr David Katz, a public health doctor from the Yale Prevention Centre in Conneticut.
I’ve never been on a diet; I regard fad diet doctors, particularly American bestselling ones, as creatures beyond contempt and those who drape their money-making activities in a robe of science as the worst sort of charlatans. So Dr Katz, a slight (and skinny) figure, was unknowingly walking into a minefield in agreeing to be interviewed by me.
His diet exploits an evolutionary device hard-wired into human brains. We are programmed to eat more if there is a variety of tastes available and to eat less if only one taste is on offer. It’s a device that drives us to seek alternative food sources, thereby making it more likely that we will get the range of nutrients we need to stay healthy.
This is because the brain is in charge of eating behaviour. The taste of our food registers in the appetite centre of the brain, lodged inside the hypothalamus which, depending on the flavours it receives, sends out signals via hormones to eat more or less. If we are eating just one food, the hypothalamus makes the taste of that food (and tastes similar to it) less pleasant and makes us feel full, thus encouraging us to stop eating and to forage for something different. If confronted with lots of tastes, the human appetite centre remains stimulated and encourages us to eat lots while the food is available.
This is called sensory specific satiety and it is the most important factor controlling how much food we eat at a meal. It’s the reason we can eat a Christmas dinner until we’re stuffed but can still say: “What’s for afters?” Our taste buds may have begun to pall on the savoury turkey and vegetables; our brain makes it taste less pleasant after the second helping. But the prospect of sweet Christmas pudding is very different and our brain allows our appetite to be stimulated once again.
We can graze endlessly at a buffet for the same reason; so many tastes leave our appetite continually restimulated. And modern food production methods are building on the principle of sensory specific satiety to encourage many of us to overeat. Many foods today contain so many ingredients and products that the brain’s appetite centre becomes confused. A savoury snack such as a sausage roll may sound simple but it is bursting with hidden flavours such as sugar and flavour enhancers.
This complexity of taste means that appetite is continually being restimulated — the brain encourages the body to have more and more of it in an attempt to maximise the nutrients seemingly on offer. The very feature designed to protect our health now threatens it.
All this informs the Flavour Point diet. Dr Katz has created a meal plan that revolves around giving people similar flavours throughout the day. So there are onion days, tomato days, sesame days and so on (see box below). Sometimes the similar flavours will be hidden, but they will have an effect on the brain and our appetite all the same. If we follow strictly, we won’t feel hungry. Or so the claim goes.
Dr Katz is is a proper academic, with a fine reputation among his peers and many publications to his name. The Yale Prevention Centre, which concentrates on studying the causes of chronic diseases, particularly diabetes, is funded by the Centres for Disease Control and Prevention and the US National Institute of Medical Health. So far, so good.
Dr Katz says he is appalled at some of the fad diet books (big tick) and was one of the most outspoken critics of the Atkins diet. “It was silly and bad nutrition. Dieting isn’t about weight loss by any means. If it were, we’d just hand cocaine to everyone.” (Cocaine is one of the most potent appetite-suppressants known.) He wanted to find a diet that was good nutrition, that didn’t ignore basic nutritional advice and that people could use easily.
In 1991 he stumbled across sensory specific satiety and was intrigued. “It’s rare that you come across something genuinely novel in medicine, but this was,” he says. The whole principle of sensory specific satiety was discovered only 30 years ago. The pioneer in the field was the American nutritionist Barbara Rolls and her husband Edmund.
In one breakthrough experiment, they gave 24 women test meals, all tasting the same and seemingly being the same, but concealing a wide variety of calories. Some were packed, others were virtually calorie-free. An hour after the meal, all the women were offered cheese and crackers (a different taste from the previous offering) and all of them ate the same amount, regardless of how high their calorie intake had been in the previous meal. Given a new taste, even the brains of those who had consumed most calories were not registering as “full”.
This is a sensory specific satiety effect. In another experiment, 32 people were fed meals that varied in taste and texture. The participants found sweet foods less pleasurable when they had recently eaten sweet foods and salty foods less pleasurable if they had recently had salty ones. It’s fairly obvious, but their research highlighted the effect for science.
Edmund Rolls, now a professor of experimental psychology at Oxford, explains the power of sensory specific satiety. “Even the smell of one food for about the time that you would normally chew it will diminish its pleasantness,” he says. Should any of you become a little overexcited at the prospect of the ultimate “sniff but don’t eat” diet, your body soon twigs that you haven’t actually eaten anything. But it is clear that this effect can be exploited and Dr Katz has done this. The central message of his diet is that by limiting flavours, your body thinks it has had enough long before it would do so if you were taking in many flavours at a time. It cuts out processed foods, which Dr Katz says are engineered to exploit the appetite stimulus that multiple flavours provide. The sort of straw- berry milkshake sold in fast food stores has recently been revealed to contain up to 59 ingredients. If you made it at home, it would contain three or four at most.
“When you taste so many flavours at once, whether from eating too many different foods or too many flavours processed into one food, you overeat before feeling full,” says Dr Katz.
It is the Flavour Point diet’s one-a-day flavour themes that he admits is the gimmick. But the idea of restricting flavours and sticking to simple foods is not. And because of the diet’s reliance on simple food, it has the benefit of sticking to the natural ingredients that are good for you anyway.
All of the recipes based around a day’s theme are calorie-counted. Most come out at about 1,500 calories a day and are low in fat, high in fibre, pay attention to glycaemic load and so on. Anyone would lose weight on such a regimen, so what makes this different? Such a low-calorie diet should also make you feel hungry and the point here is that the 20 guinea pigs Dr Katz used for his diet didn’t feel peckish.
In fact, some of the women in his study complained that they had to eat too much. And they all lost weight at the rate of about 1lb (450g) a week.
So will this diet work in the long term? I was delighted to hear Dr Katz say that he didn’t know. Honesty in a diet doc — hallelujah! But he insisted this wasn’t a fad, that it exploited a genuine phenomenon and it was food that could be eaten by the whole family.
Orange diary: a menu from the Flavour Point diet
BREAKFAST
A small bowl of wholegrain cereal with skimmed milk and a glass of 100 per cent orange juice
MID-MORNING SNACK
A small bowl of fat-free natural yoghurt with a sliced orange
LUNCH
A spinach and orange-lentil salad with feta cheese and pecans
MID-AFTERNOON SNACK
Orange and banana smoothie
DINNER
Orange cod served with green beans with orange peel, bulgar wheat and a tossed garden salad
http://www.timesonline.co.uk/newspaper/0,,175-2165257,00.html