Why we crave sweets after a meal

Have you ever experienced that weird and unexplainable desire to eat something sweet almost immediately after having a big meal? Don't worry you're not alone and there's actually a scientific explanation for the feeling. 

It turns out humans can eat more sweet things when they're already full of food and nutritional scientist Barbara Rolls from Penn State University in the United States has revealed exactly why this happens. 

The keyword is diversity. Soon after eating a large bowl of soup, we lose interest in this type of food. But if instead of another helping of soup there is a delicious lemon cake, our appetite will be rekindled.

This means that we are naturally trained to eat a variety of foods. No wonder, then, that our appetite decreases when we eat the same thing over and over again. In order to meet our nutritional needs, we need to vary the foods we eat.

Sensory-specific satiety, is a phenomenon related to the decreasing craving for a food with as you are consuming it and the subsequent resurgence of appetite after exposure to a new taste or food.

Barbara Rolls, who has researched satiety and nutrition for more than 40 years, told the Daily Mail: "So, while you might lose your appetite for that food, a different food will still be appealing. That's why you always have room for dessert."

News channel 'Vox' invited six volunteers to an experiment based on Rolls' research. The idea was to offer them food and measure their appetite for one food or another at the beginning and end of the meal.

On the first day, subjects were given a bowl of pasta to eat until they were full. When they finished, they were given another small amount of the same food. On average, participants managed to consume only one scoop of the second serving.

The experiment was repeated the next day. But this time the test subjects didn't get pasta as their second course, but instead a serving of ice cream.

The result confirmed the phenomenon of specific sensory saturation described by Barbara Rolls. The subjects ate three times more ice cream than pasta for dessert and preferred to switch ice cream flavors rather than stick to the same type.

In addition, the desire for pasta was measured on a scale from zero to ten before the first round. Participants indicated that they had an average interest of 6.2. At the end of the first round her interest dropped to 1.3 and after the second try to 0.2.

Rolls told broadcaster Vox: "Sensory-specific satiety is that change in how much you like a food, how much you want to eat as you are eating it."

Interest in ice cream, on the other hand, waned only after participants had eaten it all, not because they were full.

In a January 2020 interview with Marion Hetherington of the Society for the Study of Ingestion Behavior, Barbara Rolls stated, "These are very well-known phenomena that anyone can understand and experience."

For example, if we go to a restaurant that charges by weight, we are able to fill our plate and then have second helpings. In other words, as long as there are different types of food, our appetites tend to stay high.

An experiment by Rolls showed that, on average, people eat 60% more when there is more food choice.

But Rolls warns, "The downside is that having a wide variety of high-calorie foods can lead to overeating and potentially obesity."

Barbara Rolls (pictured) is a professor of nutrition at Penn State University and director of the Laboratory for the Study of Human Eating Behavior.

Her work focuses on issues related to satiety and obesity, and the impact of food characteristics such as variety, calorie count, and portion size across an individual's lifespan.