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New study reveals why some people are hungry all the time

Tuesday, 13 April 2021

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 others, according to experts.

These are the latest findings from PREDICT, the largest ongoing nutritional research program in the world, looking at responses to food in real life settings.

The study, which is published in Nature Metabolism, was carried out by Health Science company ZOE, which comprises a group of scientists, led by Professor Ana Valdes from the School of Medicine at the University of Nottingham.

The group of researchers (also including scientists from Harvard Medical School, King’s College London, Leeds University, and Lund University in Sweden), found why some people struggle to lose weight, even on calorie-controlled diets, and highlights the importance of understanding personal metabolism when it comes to diet and health.

Professor Ana Valdes from the School of Medicine at the University of Nottingham, who led the study team, said: “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. 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.”

Professor Ana Valdes

The scoop on blood sugar dipping:

  • More than 1,000 people took part in the study, which gathered detailed data about blood sugar responses and hunger after eating standardized and free-choice meals over two weeks.
  • Researchers found big variations between individuals in how their blood sugar levels respond to various foods.
  • People whose blood sugar levels dip significantly 2-4 hours after eating (‘big dippers’) are more likely to feel hungry sooner and consume an average of around 300 more calories over the course of the day than people with the smallest dips (‘little dippers’).
  • Whether you’re a big or little dipper is likely to be a combination of your unique biology, meal choices and activity levels.
  • Previous studies have only looked at how blood sugar rises and falls in the first two hours after eating affect hunger (blood sugar peaks), not the dips afterwards, so diet advice focused only on peaks won’t help to control your appetite.
  • Understanding your personal metabolism and choosing foods that reduce the likelihood of having big dips could help to control hunger and body weight in the long term.

In the study, “Postprandial glycaemic dips predict appetite and energy intake in healthy individuals,” the research team collected detailed data about blood sugar responses and other markers of health from 1,070 people after eating standardised breakfasts and freely chosen meals over a two week period, adding up to more than 8,000 breakfasts and 70,000 meals in total. The standard breakfasts were based on muffins containing the same amount of calories but varying in composition in terms of carbohydrates, protein, fat and fibre. Participants also carried out a fasting blood sugar response test (oral glucose tolerance test), to measure how well their body processes 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. The research team also asked people to record their 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’ 2-4 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 hunger, and waited around half an hour less, on average, before their next meal than little dippers, even though they ate exactly the same meals.

Big dippers also ate 75 more calories in the 3-4 hours after breakfast and around 312 calories more over the whole day than little dippers. This kind of pattern could potentially turn into 20 pounds of weight gain over a year.

What makes you a big dipper or a little dipper?

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, bodyweight or BMI and being a big or little dipper, although males had slightly larger dips than females on average. This is in keeping with previous findings from PREDICT showing that even identical twins can have different responses to the same foods.

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.

Lead author on the study, Patrick Wyatt from ZOE, said: “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. 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.”

Story credits

More information is available from Professor Ana Valdes from the School of Medicine at the University of Nottingham at Ana.Valdes@nottingham.ac.uk

About ZOE

ZOE is a healthcare science company helping people understand their body’s responses to food. By using machine learning combined with large scale human studies, ZOE is decoding the impact of nutrition on health. ZOE leads the PREDICT Studies and the COVID Symptom Study, which are the world’s largest community powered research programmes of their kind in nutrition and COVID-19 respectively.

Located in London and Boston, ZOE was founded by Professor Tim Spector of King’s College London, data science leader Jonathan Wolf and entrepreneur George Hadjigeorgiou. ZOE was named one of the Deloitte Fast 50 Rising Stars in 2019 for the company’s contribution to science enabled by technology and machine learning.

For more information on ZOE’s mission and science visit joinzoe.com

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The University of Nottingham is a research-intensive university with a proud heritage, consistently ranked among the world's top 100. Studying at the University of Nottingham is a life-changing experience and we pride ourselves on unlocking the potential of our students. We have a pioneering spirit, expressed in the vision of our founder Sir Jesse Boot, which has seen us lead the way in establishing campuses in China and Malaysia - part of a globally connected network of education, research and industrial engagement. The University’s state-of-the-art facilities and inclusive and disability sport provision is reflected in its status as The Times and Sunday Times Good University Guide 2021 Sports University of the Year. We are ranked eighth for research power in the UK according to REF 2014. We have six beacons of research excellence helping to transform lives and change the world; we are also a major employer and industry partner - locally and globally. Alongside Nottingham Trent University, we lead the Universities for Nottingham initiative, a pioneering collaboration which brings together the combined strength and civic missions of Nottingham’s two world-class universities and is working with local communities and partners to aid recovery and renewal following the COVID-19 pandemic.

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