If you’re always hungry between meals and can’t put your finger on the reason, new research from London has a possible answer.

A research team from King’s College London and health science company ZOE, which aims to help people understand how their bodies respond to food, discovered why it’s difficult for some people to lose weight even when using calorie-controlled diets.

Using data from PREDICT, the world’s biggest continuous nutritional research program that reviews how people react to food in real-life situations, the research team launched their study, which was published Monday in the online-only journal Nature Metabolism.

Specific information about blood sugar responses and other health markers were gathered from 1,070 people after they ate standardized breakfasts and meals they personally chose in a two-week time frame. This amounted to over 8,000 breakfasts and 70,000 meals.

Standard breakfasts were based on muffins with the same calorie count but different carb, protein and fat composition. Additionally, participants took a fasting blood sugar response test that evaluated their body’s ability to process sugar.

To measure their blood glucose levels for the entire duration of the study, participants wore adhesive continuous glucose monitors. They also monitored activity and sleep using a wearable device. Using a mobile app, they recorded their hunger, alertness and when and what they had consumed during the day.

In analyzing the data, researchers observed that some people endured noticeable “sugar dips” 2-4 hours following an initial peak. This was when their blood sugar levels quickly fell below baseline before rising up again.

Those who had significant dips were deemed “big dippers.” They had a 9% increase in hunger, and on average they waited about 30 minutes less before their next meal compared to “little dippers,” or those whose blood sugar levels didn’t dip as low. This was the case even though both participants ate the same meals.

Still, big dippers ate 75 more calories 3-4 hours following breakfast compared to little dippers. They also ate about 312 more calories during the day than little dippers.

“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,” said Dr. Sarah Berry of the School of Life Course Sciences. “We’ve now shown that sugar dips are a better predictor of hunger and subsequent calorie intake than the initial blood sugar peak response after eating, changing how we think about the relationship between blood sugar levels and the food we eat.”

Despite males on average experiencing slightly larger dips than females, researchers didn’t discover any associations between being a big dipper or little dipper and BMI, body weight or age.

“This study shows how wearable technology can provide valuable insights to help people understand their unique biology and take control of their nutrition and health,” said lead author Patrick Wyatt of ZOE. “By demonstrating the importance of sugar dips, our study paves the way for data-driven, personalized guidance for those seeking to manage their hunger and calorie intake in a way that works with rather than against their body.”