Keeping tabs on your hunger is key to successful training. If you’re pushing hard, you’re burning through more calories than usual, and you need to pay close attention to how much food you’re using to fuel those efforts to avoid an energy deficit. Similarly, if you’re toning down your training for whatever reason or trying to cut a few pounds to hit racing weight, you have to think about eating less without feeling like your energy is depleted.
But many athletes think the number of calories is all they need to measure, rather than the quality of those calories. Specifically, they should think about the satiety—or fillingness—of the foods they eat.
Satiety is the subject of a 1995 study out of Australia. The scientists fed participants 240-calorie portions of popular foods—everything from meats and potatoes to cakes and pastas. Every 15 minutes thereafter, participants reported how hungry they felt. Two hours later, the participants could eat whatever they wanted from a breakfast buffet while scientists tracked their intake—the idea being that hungrier participants would eat more at the buffet and fuller ones would eat less despite having eaten the same number of calories beforehand. In the end, the researchers came up with a quantifiable metric to measure how full different foods—from oats and whitefish to cake and french fries—will make you feel. That result is known as the satiety index.
That number differed pretty dramatically between items. Foods with lots of fat or sugar (like doughnuts or croissants) didn’t keep people full for very long, whereas the more natural, unrefined alternatives (like fruits and lean proteins) delivered high satiety numbers, says Stephan Guyenet, an obesity researcher and author of The Hungry Brain. Researchers gave each food its satiety index as compared to that of white bread, which was arbitrarily set at 100 percent. The least and most filling foods, for example, were croissants and white potatoes, with scores of 47 percent and 323 percent, respectively. Compared to a serving of equal calories of white bread, croissants are roughly half as filling, and white potatoes are more than three times as filling.
Calorie density is the key factor that predicts a food’s satiety index. In the study, less calorie-dense foods tended to be more filling because participants had to eat more volume (in ounces) to reach the same number of calories. In other words, 240 calories’ worth of lower-calorie food took up more room in their stomachs. Those foods also tend to have more fiber, so they take longer to digest.
The second metric to consider is a food’s macronutrient profile. For example, foods higher in protein and fiber kept participants fuller for longer, while those high in fat did not.
The takeaway: If you’re having trouble cramming in calories, eat foods with a lower satiety score. You’ll top off fuel reserves without feeling uncomfortably stuffed. If you’re trying to cut weight or avoid feeling hungry all the time, eat foods with a higher satiety score. They’ll help control your cravings while keeping your total calories at a lower number.
We went one step further, and used the study’s results to create a visual guide that illustrates how full a variety of foods will make you feel. The x-axis represents ounces—the amount of each food you’d have to eat to reach the 240-calorie mark. The y-axis represents satiety index—the number the food was given in the study to illustrate how filling it is compared to a 240-calorie serving of white bread. A score below 100 means the food is less filling; anything above 100 is more filling.
The higher up and to the right that a food falls, the fuller it will keep you for longer, and vice versa for foods lower and to the left.
Bakery Products
Croissants, cakes, and doughnuts registered as the least filling foods. They’re relatively calorie dense, high in fat, and rewarding only in the short-term.
Snacks and Confectionaries
Although a smidge more filling than the bakery products, most classic snacks and candies didn’t rank high on the index. The humble Mars bar was the least satiating food in this category, while fiber-rich popcorn was the most.
Carb-Heavy Foods
The right kind of carbs can be a great weight-loss tool: Plain boiled potatoes were the most filling food in the study. (Read our ode to the humble spud here.) Fatty fries, on the other hand, were the least filling of the category.
Protein-Heavy Foods
Every food in this category beat out bread. Ling fish—similar to cod—was the most filling, thanks to the large portion size required to hit 240 calories.
Fruits
Volume of the 240-calorie serving determined how full each fruit made the participants feel. Bananas, the smallest portion, registered last, while oranges, the largest portion, were most filling.
Breakfast Cereals
Refined cereals tended to score lower, while basic one-ingredient, unprocessed oatmeal was the third most-filling food in the study.