Hungry all the time? Now we know why

21st 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 the latest findings from the PREDICT study.

The results, published in Nature Metabolism, explain why some people struggle to lose weight, even on calorie-controlled diets, and highlight the importance of understanding personal metabolism when it comes to diet and health.

Dr Sarah Berry from King’s College London said:

“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. 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.”

The research

PREDICT is the largest ongoing nutritional research programme in the world that looks at responses to food in real life settings.

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.

Participants wore stick-on continuous glucose monitors (CGMs) to measure their blood sugar levels over the entire duration of the study. 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. After analysing the data however, 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.

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.”

Everyone is different

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.

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.

Tim Spector, Professor of Genetic Epidemiology at King’s College London and scientific co-founder of ZOE, concluded:

“Food is complex and humans are complicated, but our research is finally starting to open up the black box between diet and health. We’re excited to have been able to turn this cutting-edge science into an at-home nutrition and microbiome test so that everyone has the opportunity to discover their unique responses to food to best support their metabolism and gut health.”

30 key gut microbes for your health identified in landmark nutrition study

11th January 2021

The latest PREDICT results have uncovered 15 gut microbes associated with lower risks and 15 with greater risks for common conditions such as type 2 diabetes and heart disease.

The team of researchers studied thousands of stool samples and found evidence that an individual’s microbiome is linked to the specific foods they eat. Furthermore, certain microbes in the gut are linked to biomarkers of metabolic disease, and the microbiome has a greater association to these markers than other factors, such as genetics.

The research, which identified novel microbes that have not yet been named, could be used to provide personalised dietary advice for improved health.

Professor Tim Spector, who started the PREDICT study programme and is scientific founder of healthcare science company ZOE explains:

 “When you eat, you’re not just nourishing your body, you’re feeding the trillions of microbes that live inside your gut.”

The findings were published today in the prestigious journal Nature Medicine.

Eating for your gut

The PREDICT 1 study analysed detailed data on the composition of 1,100 participants’ gut microbiomes, their dietary habits and cardiometabolic blood biomarkers. 660 of our TwinsUK members took part in this study.

For example, the findings reveal that having a microbiome rich in Prevotella copri and Blastocystis species was associated with maintaining a favourable blood sugar level after a meal. Other species such as Eubacterium eligens and Roseburia sp. CAG:182 were linked to lower post-meal levels of blood fats and markers of inflammation.

Overall, the team found that diets rich in certain plant-based foods and healthy animal-based foods (e.g. oily fish, eggs and yogurt) were linked with the presence of “good” gut microbes that are associated with a lower risk of developing conditions such as obesity, type 2 diabetes and heart disease.

Conversely, diets containing more highly processed plant-based foods were more likely to be associated with “bad” gut microbes, as were diets containing less healthy animal-based foods.

This is the largest and most detailed study of its kind to uncover strong links between a person’s diet, the gut microbiome and their health, and these findings highlight the importance of food quality.

Dr Sarah Berry, from the Department of Nutritional Sciences at King’s College London said:

“As a nutritional scientist, finding novel microbes that are linked to specific foods, as well as metabolic health, is exciting. Given the highly personalised composition of each individuals’ microbiome, our research suggests that we may be able to modify our gut microbiome to optimise our health by choosing the best foods for our unique biology.”

Looking ahead

Professor Nicola Segata from the University of Trento, Italy, led the microbiome analysis. Of the findings and future research, he said:

“We were surprised to see such large, clear groups of what we informally call ‘good’ and ‘bad’ microbes emerging from our analysis.

“It is also exciting to see that microbiologists know so little about many of these microbes that they are not even named yet. This is now a big area of focus for us, as we believe they may open new insights in the future into how we could use the gut microbiome as a modifiable target to improve human metabolism and health.”

When it comes to food, one size doesn’t fit all

10th June 2019

Spaghetti on a fork with a tomato on top

What foods are best for us? People, scientists and doctors alike have been asking this question for centuries.

Today, we moved one step closer to finding the answer as the first results from the largest scientific nutrition study of its kind were announced.

The verdict: no two people’s responses to individual foods are the same – even between identical twins.

These findings demonstrate that one-size-fits-all dietary guidelines are too simplistic, and that a personalised approach to nutrition is likely to provide better long-term health benefits.

The study, which included more than 1,000 participants, was carried out by an international team led by researchers from King’s College London, Massachusetts General Hospital and nutritional science company ZOE.

Professor Tim Spector, Professor of Genetic Epidemiology at King’s College London and lead researcher on the study explained its significance:

“The sheer scale and detail of our scientific project is such that for the first time we can explore tremendously rich nutrition data at the level of an individual. Our results surprisingly show that we are all different in our response to such a basic input as food. It was a real shock to see that even identical twins have such different responses.”

The results were announced today at two prestigious international conferences.

Why did they do this research?

King’s College London is the home of TwinsUK, a long-running study looking at health and lifestyle in over 14,000 twins, led by Professor Spector.

He noticed that identical twins – who have identical genes – have very different food preferences and responses. This led him to team up with two technologists to create ZOE and set up a series of scientific studies along with King’s College London’s Department of Nutritional Sciences to look at personal responses to foods.

The company is now developing a home-based test and an app that can measure and make predictions about an individual’s nutritional responses, helping people choose the best foods for them to manage their weight and overall health.

ZOE co-founder and CEO Jonathan Wolf explained:

“For most of us, the food we eat is the most important medicine we take. And yet we are all profoundly confused about what is good for us. We believe that combining science and machine learning can solve this, by understanding for the first time our individual responses to food.”

ZOE co-founder and President George Hadjigeorgiou continued:

“We believe that everyone deserves to understand how they respond to food so that they can make confident decisions about what to eat and be in control of living a healthier and more enjoyable life.”

What did they do?

More than 1,000 volunteers – largely pairs of twins – took part in the study, called PREDICT.

Participants had to eat certain set meals and log every single item of food or drink they had for two weeks.

The researchers analysed how blood levels of sugar, insulin and fat change in response to specific meals over two weeks, along with data on activity, sleep, hunger and gut bacteria.

What did they find?

The team found that there was a wide variation in blood responses to the same meals, which is only partly explained by genes.

The proportions of nutrients such as fat, proteins and carbohydrates listed on food labels explained less than 40% of the differences between individuals’ responses to meals with similar amounts of calories.

In addition, identical twins often had different responses to identical foods, and shared just 37% of their gut bacteria – only slightly higher than the 35% shared between two unrelated individuals.

What does this mean?

These findings show how responses to food are highly individualised, and that nutritional advice needs to be tailored to each individual.

Dr Sarah Berry, Senior Lecturer in Nutritional Sciences at King’s College London and Scientific Advisor at ZOE explained:

“For the first time, we’re expanding large-scale nutritional research beyond blood sugar. These findings show that the responses to food of a number of key metabolic markers – including triglycerides, insulin and blood sugar – are highly individualised. No one has been able to combine data on this scale before.”

In addition, the results suggest that personal differences in metabolism due to factors such as gut bacteria, meal timing and exercise are just as important as the nutritional composition of foods.

Dr Andrew Chan, Professor of Medicine at Harvard Medical School and a gastroenterologist at Massachusetts General Hospital commented:

“It is reassuring that our genetic makeup only partially explains how our bodies respond to food. This underscores that our metabolism is not fixed – we have the power to change it. One exciting avenue is to tailor our diets to the bacteria in our gut that helps us metabolise nutrients.”

What’s next?

The team has now launched PREDICT 2, an expanded home-based study that is recruiting more than 1,000 participants across the US.

This will help ZOE to continue developing their technology to help people choose the best foods for them.

Find out more about the study results and the science behind them at joinzoe.com.

The word 'PREDICT' on a navy square

 

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