̽��ֱ�� of Cambridge - appetite

Brain’s ‘appetite control centre’ different in people who are overweight or living with obesity

cjb250 — Mon, 07 Aug 2023 23:01:09 +0000

̽��ֱ��researchers say their findings add further evidence to the relevance of brain structure to weight and food consumption.

Current estimations suggest that over 1.9 billion people worldwide are either overweight or obese. In the UK, according to the Office for Health Improvement & Disparities, almost two-thirds of adults are overweight or living with obesity. This increases an individual’s risk of developing a number of health problems, including type 2 diabetes, heart disease and stroke, cancer and poorer mental health.

A large number of factors influence how much we eat and the types of food we eat, including our genetics, hormone regulation, and the environment in which we live. What happens in our brains to tell us that we are hungry or full is not entirely clear, though studies have shown that the hypothalamus, a small region of the brain about the size of an almond, plays an important role.

Dr Stephanie Brown from the Department of Psychiatry and Lucy Cavendish College, ̽��ֱ�� of Cambridge, said: “Although we know the hypothalamus is important for determining how much we eat, we actually have very little direct information about this brain region in living humans. That’s because it is very small and hard to make out on traditional MRI brain scans.”

̽��ֱ��majority of evidence for the role of the hypothalamus in appetite regulation comes from animal studies. These show that there are complex interacting pathways within the hypothalamus, with different cell populations acting together to tell us when we are hungry or full.

To get around this, Dr Brown and colleagues used an algorithm developed using machine learning to analyse MRI brain scans taken from 1,351 young adults across a range of BMI scores, looking for differences in the hypothalamus when comparing individuals who are underweight, healthy weight, overweight and living with obesity.

In a study published today in Neuroimage: Clinical, the team found that the overall volume of the hypothalamus was significantly larger in the overweight and obese groups of young adults. In fact, the team found a significant relationship between volume of the hypothalamus and body-mass index (BMI).

These volume differences were most apparent in those sub-regions of the hypothalamus that control appetite through the release of hormones to balance hunger and fullness.

While the precise significance of the finding is unclear – including whether the structural changes are a cause or a consequence of the changes in body weight – one possibility is that the change relates to inflammation. Previous animal studies have shown that a high fat diet can cause inflammation of the hypothalamus, which in turn prompts insulin resistance and obesity. In mice, just three days of a fat-rich diet is enough to cause this inflammation. Other studies have shown that this inflammation can raise the threshold at which animals are full – in other words, they have to eat more food than usual to feel full.

Dr Brown, the study’s first author, added: “If what we see in mice is the case in people, then eating a high-fat diet could trigger inflammation of our appetite control centre. Over time, this would change our ability to tell when we’ve eaten enough and to how our body processes blood sugar, leading us to put on weight.”

Inflammation may explain why the hypothalamus is larger in these individuals, the team say. One suggestion is that the body reacts to inflammation by increasing the size of the brain’s specialist immune cells, known as glia.

Professor Paul Fletcher, the study’s senior author, from the Department of Psychiatry and Clare College, Cambridge, said: “ ̽��ֱ��last two decades have given us important insights about appetite control and how it may be altered in obesity. Metabolic researchers at Cambridge have played a leading role in this.

“Our hope is that by taking this new approach to analysing brain scans in large datasets, we can further extend this work into humans, ultimately relating these subtle structural brain findings to changes in appetite and eating and generating a more comprehensive understanding of obesity.”

̽��ֱ��team say more research is needed to confirm whether increased volume in the hypothalamus is a result of being overweight or whether people with larger hypothalami are predisposed to eat more in the first place. It is also possible that these two factors interact with each other causing a feedback loop.

̽��ֱ��research was supported by the Bernard Wolfe Health Neuroscience Fund, Wellcome and the NIHR Cambridge Biomedical Research Centre, with additional funding from Alzheimer’s Research UK.

Reference
Brown, SSG, et al. Hypothalamic volume is associated with body mass index. Neuroimage: Clinical; 8 Aug 2023; DOI: 10.1016/j.nicl.2023.103478

Cambridge scientists have shown that the hypothalamus, a key region of the brain involved in controlling appetite, is different in the brains of people who are overweight and people with obesity when compared to people who are a healthy weight.

Although we know the hypothalamus is important for determining how much we eat, we actually have very little direct information about this brain region in living humans

Stephanie Brown

World Obesity Federation

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Larger wine glasses may lead people to drink more

cjb250 — Mon, 06 Jun 2016 23:01:48 +0000

Alcohol consumption is one of the leading risk factors for disease and has been linked to conditions such as type 2 diabetes, cancer and liver disease. ̽��ֱ��factors that influence consumption are not clear; a recent Cochrane review published by the Behaviour and Health Research Unit (BHRU) at the ̽��ֱ�� of Cambridge found that larger portion sizes and tableware increased consumption of food and non-alcoholic drinks, but found no evidence relating to consumption of alcohol.

To examine whether the size of glass in which alcohol is served affects consumption, the team at the BHRU, together with Professor Marcus Munafo from the ̽��ֱ�� of Bristol, carried out a study in ̽��ֱ��Pint Shop in Cambridge from mid-March to early July 2015. ̽��ֱ��establishment has separate bar and restaurant areas, both selling food and drink. Wine (in 125ml or 175ml servings) could be purchased by the glass, which was usually a standard 300ml size.

Over the course of a 16-week period, the owners of the establishment changed the size of the wine glasses at fortnightly intervals, alternating between the standard (300ml) size, and larger (370ml) and smaller (250 ml) glasses.

̽��ֱ��researchers found that the volume of wine purchased daily was 9.4% higher when sold in larger glasses compared to standard-sized glasses. This effect was mainly driven by sales in the bar area, which saw an increase in sales of 14.4%, compared to an 8.2% increase in sales in the restaurant. ̽��ֱ��findings were inconclusive as to whether sales were different with smaller compared to standard-sized glasses.

“We found that increasing the size of wine glasses, even without increasing the amount of wine, leads people to drink more,” says Dr Rachel Pechey from the BHRU at Cambridge. “It’s not obvious why this should be the case, but one reason may be that larger glasses change our perceptions of the amount of wine, leading us to drink faster and order more. But it’s interesting that we didn’t see the opposite effect when we switched to smaller wine glasses.”

Professor Theresa Marteau, Director of the Unit, adds: “This suggests that avoiding the use of larger wine glasses could reduce the amount that people drink. We need more research to confirm this effect, but if it is the case, then we will need to think how this might be implemented. For example, could it be an alcohol licensing requirements that all wine glasses have to be below a certain size?”

̽��ֱ��research was funded by the Department of Health.

Reference
Pechey, R et al. Does wine glass size influence sales for on-site consumption? A multiple treatment reversal design. BMC Public Health; 7 June 2016; DOI: 10.1186/s12889-016-3068-z

Selling wine in larger wine glasses may encourage people to drink more, even when the amount of wine remains the same, suggests new research from the ̽��ֱ�� of Cambridge. In a study published today in the journal BMC Public Health, researchers found that increasing the size of wine glasses led to an almost 10% increase in wine sales.

It’s not obvious why this should be the case, but one reason may be that larger glasses change our perceptions of the amount of wine, leading us to drink faster and order more

Rachel Pechey

BMC Public Health

Wine glasses at ̽��ֱ��Pint Shop

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Genetic variant may help explain why Labradors are prone to obesity

cjb250 — Tue, 03 May 2016 15:57:14 +0000

In developed countries, between one and two in three dogs (34-59%) is overweight, a condition associated with reduced lifespan, mobility problems, diabetes, cancer and heart disease, as it is in humans. In fact, the increase in levels of obesity in dogs mirrors that in humans, implicating factors such as reduced exercise and ready access to high calorie food factors. However, despite the fact that dog owners control their pets’ diet and exercise, some breeds of dog are more susceptible to obesity than others, suggesting the influence of genetic factors. Labradors are the most common breed of dog in the UK, USA and many other countries worldwide and the breed is known as being particularly obesity-prone.

In a study published today in the journal Cell Metabolism, an international team led by researchers at the Wellcome Trust-Medical Research Council Institute of Metabolic Science, ̽��ֱ�� of Cambridge, report a study of 310 pet and assistance dog Labradors. Independent veterinary professionals weighed the dogs and assessed their body condition score, and the scientists searched for variants of three candidate obesity-related genes. ̽��ֱ��team also assessed ‘food motivation’ using a questionnaire in which owners reported their dog’s behavior related to food.

̽��ֱ��researchers found that a variant of one gene in particular, known as POMC, was strongly associated with weight, obesity and appetite in Labradors and flat coat retrievers. Around one in four (23%) Labradors is thought to carry at least one copy of the variant. In both breeds, for each copy of the gene carried, the dog was on average 1.9kg heavier, an effect size particularly notable given the extent to which owners, rather than the dogs themselves, control the amount of food and exercise their dogs receive.

“This is a common genetic variant in Labradors and has a significant effect on those dogs that carry it, so it is likely that this helps explain why Labradors are more prone to being overweight in comparison to other breeds,” explains first author Dr Eleanor Raffan from the ̽��ֱ�� of Cambridge. “However, it’s not a straightforward picture as the variant is even more common among flat coat retrievers, a breed not previously flagged as being prone to obesity.”

̽��ֱ��gene affected is known to be important in regulating how the brain recognises hunger and the feeling of being full after a meal. “People who live with Labradors often say they are obsessed by food, and that would fit with what we know about this genetic change,” says Dr Raffan.

Senior co-author Dr Giles Yeo adds: “Labradors make particularly successful working and pet dogs because they are loyal, intelligent and eager to please, but importantly, they are also relatively easy to train. Food is often used as a reward during training, and carrying this variant may make dogs more motivated to work for a titbit.

“But it’s a double-edged sword – carrying the variant may make them more trainable, but it also makes them susceptible to obesity. This is something owners will need to be aware of so they can actively manage their dog’s weight.”

̽��ֱ��researchers believe that a better understanding of the mechanisms behind the POMC gene, which is also found in humans, might have implications for the health of both Labradors and human.

Professor Stephen O’Rahilly, Co-Director of the Wellcome Trust-Medical Research Council Institute of Metabolic Science, says: “Common genetic variants affecting the POMC gene are associated with human body weight and there are even some rare obese people who lack a very similar part of the POMC gene to the one that is missing in the dogs. So further research in these obese Labradors may not only help the wellbeing of companion animals but also have important lessons for human health.”

̽��ֱ��research was funded by the Wellcome Trust, the Medical Research Council and the Dogs Trust.

Reference
Raffan, E et al. A deletion in the canine POMC gene is associated with weight and appetite in obesity prone Labrador retriever dogs. Cell Metabolism; 3 May 2016; DOI: 10.1016/j.cmet.2016.04.012

A genetic variation associated with obesity and appetite in Labrador retrievers – the UK and US’s favourite dog breed – has been identified by scientists at the ̽��ֱ�� of Cambridge. ̽��ֱ��finding may explain why Labrador retrievers are more likely to become obese than dogs of other breeds.

People who live with Labradors often say they are obsessed by food, and that would fit with what we know about this genetic change

Eleanor Raffan

Thomas Hawk

Where's My Snacks? (crop)

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