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.”

Gut bacteria need each other – and that affects our metabolism

3rd October 2019 – by Paz Garcia

Pile of lego bricks
Gut bacteria work together like Lego

Teamwork is key for the trillions of bacteria that live in our gut and this has a big impact on our metabolism, according to new research led by King’s College London, published today in Nature Communications.

The human gut is home to bacteria that help us digest our food, produce vitamins and perform many other tasks that influence our health.

Gut bacteria work together in groups to carry out different functions. The researchers, led by the Department of Twin Research & Genetic Epidemiology, found that this teamwork is much more important and more closely linked with our metabolism than individual species of bacteria.

The researchers studied the gut bacteria, blood and stool of over a thousand twins who take part in TwinsUK. This allowed the team to run the first large study on the link between gut bacterial species, their functions and the metabolism in the gut and blood of the participants.

The team found that while unrelated people share only 43% of gut bacteria species, they still share 82% of functions carried out by groups of gut bacteria. This is because different bacterial species can contribute to the same function and so different groups can work together to can carry out similar activities.

This research therefore suggests that health treatments designed to target gut bacteria – and our metabolism – should focus on groups of gut bacteria that carry out a particular function, rather than individual bacterial species.

Senior author Dr Mario Falchi explained:

“We can think of our gut bacteria like Lego bricks – the colour of the bricks doesn’t matter as much compared with how they fit together to make something. With gut bacteria, the individual species don’t matter as much as the group working together to carry out a function.”

“This is the first large study to explore the metabolic potential of the entire gut bacteria ecosystem. Our findings underline the importance of studying groups of bacteria and their functions overall, rather than focusing on specific species. These results add to the growing body of evidence that gut bacteria are intrinsically linked with human health.”

*

Visconti A, Le Roy CI, Rosa F, Rossi N, Martin TC, Mohney RP, Li W, de Rinaldis E, Bell JT, Venter JC, Nelson KE, Spector TD and Falchi M. Interplay between the human gut microbiome and host metabolism. Nature Communications (2019).

Type 2 diabetes study puts the kidney, spleen and the eyes in the spotlight

10th June 2019 – by Paz Garcia

A new study has identified over 60 differences in molecules in 18 organs of type 2 diabetic mice.

The research found that there are more significant changes in the kidney, spleen and eyes, pointing to a faster deterioration of these organs.

Hands using a lancet to prick a finger. Blood glucose meter in background.
Researchers are working to develop better treatments for people with type 2 diabetes

This study is the most comprehensive understanding we have of metabolic changes in specific organs of this mouse model of type 2 diabetes and establishes a new reference for further research.

This work will therefore help researchers to develop better treatments for people living with type 2 diabetes, and therapies to prevent people ever developing the condition.

The work was led by Dr Marina Mora-Ortiz from the Department of Twin Research and Genetic Epidemiology, King’s College London.

Why did they do this research?

All types of diabetes affect an estimated 422 million people around the world, with cases increasing every day. The vast majority of cases are due to type 2 diabetes, which is a metabolic condition in which the body struggles to process sugar in the blood, and it can lead to serious complications that affect the eyes, heart, kidneys and limbs.

Although we know type 2 diabetes is a metabolic condition, there hasn’t been a systematic study of the metabolic changes which occur as the condition progresses.

The researchers wanted to develop a better understanding of the metabolic processes involved in the development of the condition, so that we can develop better treatments.

Dr Mora-Ortiz and her colleagues therefore decided to study the changes in metabolism in special model mice commonly used to study type 2 diabetes.

This is the first time that researchers have carried out this type of analysis in such a large number of organs in this model mouse, known as the db/db mouse.

What did they do?

The team studied 18 different parts of the body in six diabetic mice and in six regular mice for comparison.

The researchers used a powerful technique known as NMR spectroscopy to determine the levels of certain metabolites – molecules involved in metabolism – in each of these body parts.

The team found 61 changes in metabolites associated with type 2 diabetes. The kidney, spleen and eye had the most differences in metabolites when compared with mice without diabetes.

What does this mean for type 2 diabetes?

Dr Marina Mora-Ortiz, who led the research, explained:

“This work will help us to understand better which organs are more seriously affected by type 2 diabetes. We know now, for example, that further research should focus in the spleen which is an important organ of the immune system and has been traditionally neglected in diabetes research.”

What’s the next step?

In their paper, the authors say that future studies should consider the impact of diet and the environment on the changes in metabolites associated with type 2 diabetes.

Full citation:

Mora-Ortiz, M., Nuñez Ramos, P., Oregioni, A., Claus, S.P. (2019). “NMR metabolomics identifies over 60 biomarkers associated with Type II Diabetes impairment in db/db mice”. Metabolomics. (DOI: 10.1007/s11306-019-1548-8)

 

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