Being able to make room for dessert even when we’ve eaten our fill at a meal has been dubbed the “dessert stomach” or “second stomach”. Of course, we humans only have one stomach, and being tempted by the dessert menu isn’t because we have another stomach. It’s a result of how our appetite system works.
In their book outlining how to lose weight by moving to less energy dense foods** Rolls and Barnett dedicate a chapter to variety in our diet. Barbara Rolls is one of the world’s leading researchers into eating and appetite and she tells the story of an Italian feast she attended where 14 (yes 14) pasta courses preceded dessert. “Each was exquisitely prepared, aromatic, mouth-watering. Yet by the middle of the meal all but the heartiest eaters had given up”. Apparently Professor Rolls and her fellow diners abandoned the table and instead chatted and drank, ignoring the last 6 or 7 pasta dishes.
But when dessert arrived, suddenly everyone was interested. They sat down and tucked in. Professor Rolls tells this story to illustrate “taste-specific satiety” – the way we find successive mouthfuls of the same food, or the same sort of food, less pleasant. It’s one of the mechanisms which helps us stop eating, and it generalises to similar foods. Sweet foods affect how appealing other sweet foods seem, and salty foods affect the appeal of other salty foods.
Variety is the spice of life!
Rolls and Barnett explain that the variety effect starts very young. Babies respond to variety – when a breast-feeding mother varies her diet, eating foods that change the flavour of her milk, her baby will drink more milk than when she has a blander diet with little variation.
And when it comes to adults, Professor Rolls found that when people had sandwiches with 4 different fillings, they ate a third more than when they had just their favourite filling in all of the sandwiches. This is potentially a really useful thing for us to be aware of if we’re trying to eat in moderation. Particularly when it comes to how many different calorific snacks we keep in the kitchen.
Too much of a good thing
Even your favourite food loses its appeal if you just keep eating it on its own. Rolls and Barnett say it’s the amount you eat of a particular food that determines your satiety. So if the food you are eating is lower in energy density, the taste-specific satiety for that food will kick in after you’ve consumed fewer calories.
Why did we evolve taste-specific satiety?
It’s thought that TSS evolved to ensure that we eat a balanced diet and consume all the nutrients we need.
How to make the variety effect work for you
Rolls and Barnett spell out how you can use the variety effect to help you manage your weight. As they say, restrictive diets partly achieve weight loss by making your eating really monotonous. When there is very little variety you will naturally eat less. Turn this to your advantage – having just one type of calorie-dense food in the house rather than several will avoid the temptation to eat a variety of high calorie snacks. You may love Pringles, but if it’s the only savoury snack you have in the house, you’ll consume fewer calories from savoury snacking than if you had a whole range of salty snacks to graze through.
At the same time, having a range of lower energy dense foods available means you’re more likely to find something you fancy than if you only have one or two. And once you’ve had enough of the first food you can move onto another that you’ll still have an appetite for.
Rolls, B. and Barnett, R (2000) The Volumetrics Weight Control Plan. HarperTorch publishers New York.