Giles Yeo, PhD
Giles Yeo, PhD, is principal research associate, Metabolic Research Laboratories & MRC Metabolic Diseases Unit, University of Cambridge, United Kingdom, and the author of Why Calories Don’t Count.
The morning after the ball drops in Times Square, many of us begin to consider our New Year’s resolutions. More often than not, one of the goals is to lose a few pounds.
There is no magical one-size-fits-all solution, but there are three biological principles that may make choosing a diet that suits you easier:
1. To lose weight, you need to eat less.
2. Food that takes longer to digest will travel further down the gut, which results in a release of hormones that make you feel fuller. If you feel fuller, you will eat less and will lose weight.
3. Foods have different levels of caloric availability, which is the number of usable calories we can get out of a food.
The two components of food that take the longest to digest and have the lowest caloric availability are protein and fiber.
Protein is the most chemically complex macronutrient, so your body uses more time and energy to digest and metabolize it. It has a caloric availability of 70 percent, which means that for every 100 calories of protein that you consume, you use only 70 because you spend 30 on metabolism. By comparison, fat has a caloric availability of 98 percent. Complex carbohydrates (whole grains, vegetables), have 90 percent availability, while refined carbohydrates (white flour, white sugar) have 95 percent. This is why a calorie of protein makes you feel fuller than a calorie of fat or carbohydrate, and why high-protein diets work well for some people.
Fiber is a type of plant-based carbohydrate that is structured in a way that humans cannot digest. From the perspective of caloric availability, it slows down the rate of digestion, which causes the release of nutrients over a longer period of time and reduces the absolute number of calories absorbed.
An illustration of the impact of fiber can be seen when you compare drinking a glass of orange juice to eating an orange. When you drink OJ, the sugar, which, incidentally, is at the same concentration as that of soda, is absorbed almost immediately. When you eat an orange, however, the sugar is interlocked in the fiber, so it takes energy and time for our digestive system to extract it, thus we feel fuller. This is why dietary approaches that are high in fiber, including plant-based, low-glycemic index, and Mediterranean plans, work for weight loss.
People often say that 95 percent of diets don’t work, which is not technically true. A more accurate statement is that 95 percent of diets are ones we can’t stick to. Losing weight (which is the easier part of the process) and keeping it off (this is undoubtedly the more difficult part) requires a long-term change to one’s eating behavior and pattern.
Whatever approach you choose can’t be extreme, because then it won’t be sustainable. It also has to suit your life situation: What can you afford? Do you have kids? Do you work shifts? How do you get to work? What foods do you enjoy?
Keep it simple: Eat adequate protein—about 16 percent of your total daily intake—from either animal or plant-based sources, and try to include as much fiber as possible. That’s the foundation of a healthy, effective, and (hopefully) sustainable weight-loss diet.
