African genomic variant associated with obesity
An international team of scientists have identified a genomic variant which predisposes Africans and African-Americans to obesity. Many genomic studies thus far have focused on Europeans, whilst across the USA, African-Americans have the highest age-adjusted rates for obesity. The researchers used a genome-wide association study (GWAS) to investigate this, as well as the genomic effects in continental Africans. A GWAS compares the genomes of people with a health condition to those that do not. In this study, the gene semaphorin-4D (SEMA4D) was identified, which is absent in both Europeans and Asians.
Due to the dearth in research in people of African descent, this study has been recognised as one of the first to perform a GWAS for this particular issue. The findings may also help to explain how the African environment can influence specific genes in the context of obesity risk. The authors hope to replicate their findings in larger populations and use animal models to further assess the effect of SEMA4D.
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The European change in fat metabolism from ancient to modern times
Recently, evolutionary biologists have been looking into how changes in diet have led to human adaptations to genes that regulate fat metabolism. There are two essential genes that regulate the synthesis of vital fatty acids, fatty acid desaturase 1 and 2 (FADS 1 and 2). They change dietary fats into components for use in the heart and brain. Previously, scientists have shown that the FADS genes are commonly targets of natural selection, as variants appear associated with changes in dietary patterns. In this study data from 101 Bronze Age individuals and present-day human data are examined. Recent adaptive mutations in the FADS genes were analysed to determine which mutations might have been selected for.
They found that certain single DNA mutations have been targeted to increase the production of the long-chain PUFAS, arachidonic and eicosapentaenoic acid. This is similar to a change seen in the Indian population, whose diet is heavily vegetarian. It is therefore hypothesised that the European population may be in the process of adapting to a diet rich in fatty acids derived from plant sources, whilst moving away from those derived from animal sources. It is thought that the introduction of agriculture and its high uptake in Europe has contributed to this shift, as more people have been consuming grains and other plant-derived foods. They performed further research whose results suggested that these changes in PUFA production led to an improved cholesterol level. It is hoped that more research into the FADS region may help to develop individualised diets in the future.
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Long-term stress linked to higher risk of obesity
Research from University College London has concluded that people who suffer from long-term stress may be more prone to obesity. Researchers in this study analysed hair samples of 2,527 individuals aged 54 and older. They measured the levels of cortisol, known as the stress hormone, in these samples taking data over a four year period, they also measured BMI and waist circumference. They were then able to match the levels of cortisol to the persistence of obesity over time (as 2cm of hair represents approximately 2 months of growth).
They found that individuals with particularly higher levels of cortisol in their hair tended to have higher waist circumferences and BMIs. Chronic stress has been linked to obesity before, with people reporting overeating and ‘comfort eating’ high sugar and fat foods in times of stress, however this study has helped provide consistent evidence of this link. The study did have some limitations however, the data was from an exclusively older population, where levels of cortisol will be different to their younger counterparts, and causality cannot be interpreted from the results, only that there is a correlation. The researchers are therefore hoping to continue their research to further understanding in this area.
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Physical activity has higher benefit the older you are
The results of an observational study have been published in the European Journal of Preventive Cardiology. They show that the benefits of physical activity may outweigh the impact of obesity on cardiovascular disease. Data was collected on 5,344 individuals aged between 55 and 97, who were all free from cardiovascular disease at baseline. At the time, information on BMI, physical activity, smoking, alcohol use, diet, and education was taken. Over the course of 15 years the participants were followed and 16% of them suffered a cardiovascular event.
When the data was analysed it was found that physical activity was associated with a decreased risk of cardiovascular disease, regardless of what the individual’s BMI was. The results show that physical activity plays a crucial role in the health of middle aged and elderly people and is protective against the harmful effects of overweight and obesity. As the participants were all taken from The Rotterdam Study there were already parameters set for ‘low’ and ‘high’ amounts of physical activity, this was translated to two and four hours of daily activity – which itself included anything from biking to housework. The researchers hope to show that any physical activity is beneficial in terms of cardiovascular risk, even in those that are already normal weight or elderly.
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Sugars can pass through breast milk
Researchers from the University of Southern California have found that fructose, a sugar that is linked to obesity and diabetes, can be passed from mother to baby via breast milk. The study itself involved 25 mothers and infants and also found that even a small amount of fructose daily could be associated with increased body weight. The sugar itself is found in fruit and processed food and beverages, it is not found naturally in breast milk, instead it is derived from the mother’s diet.
Exposing these children to higher amounts of sugar during growth and development can lead to problems with cognitive development as well as lifelong risks of obesity, diabetes, heart, and fatty liver disease. Unfortunately, the researchers of this study did not collect dietary data from the mothers so were unable to correlate the types of foods that the mothers consume to the levels of fructose in their breast milk, they are now undertaking this stage of their research. They are also keen to highlight the fact that caregivers should be aware and prepared to give advice to mothers about what sugars they do consume during pregnancy.
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Exercise-induced hormone involved in bone metabolism
Irisin, a fat-burning, exercise-induced hormone has been shown to increase the formation and thickness of bone in mice. Researchers from Tufts University observed that after two weeks of voluntary wheel running mice expressed more of the hormone, further to this, when the hormone was administered systemically, the same bone effects were seen. This research is helping to further our understanding of how beneficial exercise might be for the skeletal system. Irisin has already been shown to convert white fat tissue into calorie-burning brown fat, it has also been shown to improve glucose intolerance, however little is known about where the hormone is produced.
The researchers in this study were able to isolate irisin and found that it was expressed in several different bone regions. They also found that irisin can directly increase the production of osteoblasts – cells that synthesise bone – and inhibit the production of osteoclasts – cells that break down bone. This study has shown that whilst irisin is capable of promoting the browning of white adipose tissue, it is also involved in the regulation of bone metabolism, the researchers are hoping to investigate it’s effects more thoroughly to assess its therapeutic potential.
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The heavier you are the slimmer your chances of receiving hospice care
A new study from the University of Michigan has found that the heavier a person is, the less likely they are to receive a place at a hospice or die at home. The researchers analysed data from 5,677 elderly people taking part in a long-term health study. They found that people with a higher BMI were not only less likely to use a hospice, but when they did they were in it for less time than their normal weight counterparts. The findings have become pertinent as the increasingly overweight American population ages.
The study itself did not analyse the reasons why people with obesity received less hospice care, but the researchers did put forward several factors. Normally, it takes a larger team to care for an overweight individual due to the co-morbidities associated with increased weight, furthermore obesity may mask the changes that signpost to clinicians when a person should begin to receive hospice care. For example, a major change in body weight is generally more noticeable in leaner individuals, cachexia (‘wasting away’) is a common sign seen towards the end of a person’s life. The researchers also suggest that there is a bias against people who are overweight amongst healthcare professionals, however they were not able to measure this phenomenon during their study, this is something they are hoping will be investigated in the future.
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T2DM prevented in 80% of at-risk patients
A team from Imperial College London have repurposed the drug liraglutide and have found that it can help to prevent the progression of ‘prediabetes’ to diabetes. Prediabetes itself is characterised by slightly increased blood sugar levels and can often lead to T2DM, it is curable with exercise and a healthier diet, but once it progresses to diabetes it is significantly harder to treat. Liraglutide is already used to treat obesity and diabetes – it works by activating the areas of the brain that control appetite and eating – however researchers found that when combined with diet and exercise it can help prevent progression to diabetes in those that are prediabetic.
The study itself included 2,254 obese adults across 27 countries; they were split into two groups, with one group administered liraglutide via injection, alongside diet and exercise, whilst the other group did not receive any medication. They found that the patients given liraglutide were 80% less likely to develop diabetes than those in the placebo group. The drug was also linked to greater sustained weight loss over the course of three years. The researchers are particularly excited at the fact that treatment with liraglutide could save the healthcare system millions by preventing diabetes developing in many people.
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Genetic link between body shape and heart disease
A study originating from Massachusetts General Hospital has found that a pattern of gene variants associated with certain body shapes increases the risk of T2DM as well as heart disease. This ‘apple-shape’ describes when weight is commonly deposited around the abdomen, rather than the hips and thighs. The researchers were aiming to discover whether a genetic predisposition to abdominal adiposity was associated with the risk of T2DM and coronary heart disease, they concluded that it certainly does.
Due to the many factors that contribute to the development of heart disease the researchers had to employ a method called Mendelian randomisation, which measures whether an inherited gene variant can cause the development of a disease. They used previous research which identified 48 different gene variants as responsible for abdominal adiposity and developed a genetic risk score. They combined this with data from the UK Biobank to determine any association. Whilst they found an association between genetic predisposition to abdominal adiposity and heart disease, they did not find any between lifestyle factors and genetic risk score. This therefore confirmed that the gene variants responsible for body shape were associated with cardiometabolic risk. The results may allow physicians to use body shape as a predictor for heart disease and T2DM in the future, however further research must be undertaken to identify any other gene variants that may be responsible.
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Childhood weight is 35-40% inherited
A new study from the University of Sussex has found that 35-40% of a child’s BMI is inherited from their parents. For obese children this proportion rises to approximately 55-60%. The research used data from 100,000 children and their parents across the globe and found that intergenerational transmission of BMI is around 0.2, or 20% each from the mother and father. Interestingly, the results were consistent across the different countries, with varying lifestyle factors coming into play, suggesting that this is not just an isolated phenomenon.
The study also found that the effect was more pronounced when a child was heavier. The ‘parental effect’ was higher in more obese children; for thin children, the association is likely to be 10% each from the mother and father, for the heavier child this could go up to 30%. The results highlight that obesity is not only due to lifestyle factors but also genetic and family factors, and therefore it may be wise to monitor the weight of children especially if their parents are overweight or obese.
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Body shaming linked to multiple health risks
People who suffer from obesity are often the subject of stereotyping from the people around them. A new study published in Obesity has described how this form of prejudice can actually increase the risk of cardiovascular and metabolic disease amongst people with obesity. Some schools of thought support the theory that stigma can help motivate the individuals to lose weight, however this study has found that it might in fact have the opposite effect. The research involved 159 adults with obesity who completed questionnaires measuring depression, body shaming and the internalisation of this stigma.
It was found that ‘weight bias internalisation’ (which occurs when people apply negative stereotypes to themselves – such as laziness) and diagnosis of metabolic syndrome correlated. Furthermore, those who had been subject to body shaming were more likely to internalise weight bias, and therefore this exacerbated their weight problem. Dr Tom Wadden, co-author of the study, wanted to highlight that health care providers and the media play an important role in promoting weight loss and should therefore be aware that shaming people will have a negative effect on their overall health; in summary, patients with obesity need to be treated with respect and supported in order to improve their health and bring them back to a healthy weight.
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New guidelines on paediatric obesity
The Endocrine Society has published a new set of guidelines to cover the prevention, treatment, and assessment for paediatric obesity. In the USA paediatric obesity costs an estimated £14.1 billion covering drugs prescriptions, emergency visits as well as outpatient appointments. Therefore there is a drive to identify those children at risk and the address these risks appropriately.
The clinical guidelines provide recommendations on how to evaluate children for medical and psychological complications. They also provide information on when to evaluate children for rare genetic causes of obesity, as well as when to consider medication and different surgical techniques for adolescents. The guidelines state that around 7% of children with severe obesity may suffer from a rare genetic mutation, and specific testing should be carried out if there is early onset obesity (before 5 years of age), an increased drive to eat food, or a family history of severe obesity.
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