A new study shows that people who experience big dips in blood-sugar levels several hours after eating end up feeling hungrier and consuming hundreds more calories during the day than those whose blood-sugar levels are more consistent.

The study, published in Nature Metabolism, is from PREDICT, the largest ongoing nutritional research program in the world that looks at responses to food in real-life settings. The PREDICT studies are led by scientists at Massachusetts General Hospital, Stanford Medicine, Harvard T.H. Chan School of Public Health and, for this particularly study, King’s College London.

The research team collected detailed data about blood-sugar responses and other markers of health from 1,070 people after eating standardized breakfasts and freely chosen meals over a two-week period, adding up to more than 8,000 standardized breakfast meals and more than 71,000 ad libitum free-living meals. The standardized breakfasts were based on muffins containing the same number of calories but varying in macronutrient composition (i.e., high carbohydrate, high protein, high fat and high fiber). Participants also observed blood-sugar levels using a fasting blood-sugar response test (oral glucose tolerance test) both before and after meals to measure how well their bodies process sugar.

Participants wore stick-on continuous glucose monitors (CGMs) to measure their blood-sugar levels over the entire duration of the study, as well as a wearable device to monitor activity and sleep. They also recorded levels of hunger and alertness using a phone app, along with exactly when and what they ate over the day.

Previous studies looking at blood sugar after eating have focused on the way that levels rise and fall in the first two hours after a meal, known as a blood sugar peak. However, after analyzing the data, the PREDICT team noticed that some people experienced significant “sugar dips” two to three hours after this initial peak, where their blood-sugar levels fell rapidly below baseline before coming back up.

Big dippers had a 9% increase in reported hunger, and waited about 24 minutes less, on average, before their next meal than little dippers, even though they ate exactly the same standardized meals. Big dippers also ate 75 more calories in the three to four hours after breakfast and around 312 calories more over the whole day than little dippers. This kind of pattern could potentially turn into as much as 30 pounds of weight gain over a year.

Comparing what happens when participants eat the same test meals revealed large variations in blood-sugar responses between people. The researchers also found no correlation between age, body weight or body mass index (BMI) and being a big or little dipper, although males had slightly larger dips than females on average.

What the Research Means to Health and Exercise Professionals

It has long been suspected that blood-sugar levels play an important role in controlling hunger, but the results from previous studies have been inconclusive. The researchers of this study believe their results show that sugar dips are a better predictor of hunger and subsequent calorie intake than the initial blood-sugar peak response after eating. According to Dr. Sarah Berry, a nutrition scientist at King’s College London and one of the study’s researchers, this is changing how we think about the relationship between blood-sugar levels and the food we eat.

“Many people struggle to lose weight and keep it off, and just a few hundred extra calories every day can add up to several pounds of weight gain over a year,” Professor Ana Valdes from the School of Medicine at the University of Nottingham, who led the study team, says. “Our discovery that the size of sugar dips after eating has such a big impact on hunger and appetite has great potential for helping people understand and control their weight and long-term health.”

There was also some variability in the size of the dips experienced by each person in response to eating the same meals on different days, suggesting that whether you’re a dipper or not depends on individual differences in metabolism, as well as the day-to-day effects of meal choices and activity levels.

So, if people can respond differently to the exact same meals, how can you help your clients figure out what works for them? An easy way to start is to encourage your clients to pay attention to the foods they eat and how different foods and meals make them feel. Becoming more aware of hunger and alertness feelings can lead to making healthier choices that keep alertness levels higher for longer and hunger levels lower for longer. Keeping a food diary, even for just a few days, can provide real insight into which foods make a person feel good and which ones leave them ready for a nap. And remind them that following the basics of healthy eating, such as eating fewer refined carbohydrates and processed foods, drinking enough water, choosing more whole foods, and including high-quality proteins and fats at each meal, may help them feel fuller for longer and eat less overall.