Sitting in front of the TV puts kids in the obesity hotseat
February 8, 2019
Science Daily/University of South Australia
The simple act of switching on the TV for some downtime could be making a bigger contribution to childhood obesity than we realize, according to new research.
The study investigated the impact of different sitting behaviours -- watching television, playing video games, playing computer, sitting down to eat, or travelling in a car -- and found that watching TV is more strongly associated with obesity in both boys and girls than any other type of sitting.
While childhood obesity is a global issue, data from the Australian Bureau of Statistics 2017-18 show that in Australia almost a quarter of children aged 5-17 years are considered overweight or obese.
UniSA researcher, Dr Margarita Tsiros says the study provides new insights about the impact of sedentary behaviours on children.
"It's no surprise that the more inactive a child is, the greater their risk of being overweight," Dr Tsiros says.
"But not all sedentary behaviours are created equal when it comes to children's weight. This research suggests that how long children spend sitting may be less important that what they do when they are sitting.
"For instance, some types of sitting are more strongly associated with body fat in children than others, and time spent watching TV seems to be the worst culprit."
The study assessed the sedentary behaviours of 234 Australian children aged 10-13 years who either were of a healthy weight (74 boys, 56 girls) or classified as obese (56 boys, 48 girls).
It found that, excluding sleep, children spent more than 50 per cent of their day sitting, with television dominating their time for 2.5 -- 3 hours each day.
Dr Tsiros says that the study also found differences between the sitting behaviours of boys and girls.
"Boys not only watched more TV than girls -- an extra 37 minutes per day -- but also spent significantly more time playing video games," Dr Tsiros says.
"Video gaming and computer use are popular past times, but our data suggests these activities may be linked with higher body fat in boys.
"Boys who are sitting for longer than 30 minutes may also have higher body fat, so it's important to monitor their screen and sitting time and ensure they take regular breaks."
Dr Tsiros says that setting children up on a path towards a healthy weight is extremely important to their health now and in the future.
"When we look at adult obesity, almost two thirds of Australians are overweight or obese, which is causing many serious health issues," Dr Tsiros says.
"An overweight child is more likely to grow up into an overweight adult, so the importance of tackling unhealthy behaviours in childhood is critical.
"Children who are obese have an increased risk of developing serious health disorders, including type 2 diabetes, high blood pressure and cholesterol.
"They may also experience reduced wellbeing, social and self-esteem issues, along with pain and difficulties with movement and activity.
"By understanding children's sedentary behaviours -- especially those that are placing our kids at risk -- we'll ensure they stay on a better path towards a healthier weight."
https://www.sciencedaily.com/releases/2019/02/190208085857.htm
Fruit and vegetables may be important for mental as well as physical well-being
Consuming more fruit and vegetables can improve your mental well-being, according to a new study.
February 5, 2019
Science Daily/University of Leeds
Researchers have analyzed data from more than 40,000 people in the UK, and found that changes in fruit and vegetable consumption are correlated with changes in mental well-being.
A key feature of this work is that the study was able to follow the same individuals over time.
The study also controlled for alternative factors that may affect mental well-being, such as age, education, income, marital status, employment status, lifestyle and health, as well as consumption of other foods such as bread or dairy products.
The research showed a positive association between the quantity of fruit and vegetables consumed and people's self-reported mental well-being.
Specifically, the findings indicate that eating just one extra portion of fruits and vegetables a day could have an equivalent effect on mental well-being as around 8 extra days of walking a month (for at least 10 minutes at a time).
Dr Neel Ocean of the University of Leeds, who authored the study with Dr Peter Howley (University of Leeds) and Dr Jonathan Ensor (University of York), said: "It's well-established that eating fruit and vegetables can benefit physical health.
"Recently, newer studies have suggested that it may also benefit psychological well-being. Our research builds on previous work in Australia and New Zealand by verifying this relationship using a much bigger UK sample.
"While further work is needed to demonstrate cause and effect, the results are clear: people who do eat more fruit and vegetables report a higher level of mental well-being and life satisfaction than those who eat less."
Dr Howley said: "There appears to be accumulating evidence for the psychological benefits of fruits and vegetables. Despite this, the data show that the vast majority of people in the UK still consume less than their five-a-day.
"Encouraging better dietary habits may not just be beneficial to physical health in the long run but may also improve mental well-being in the shorter term."
Dr Ensor added: "This work is part of a broader project between our universities known as "IKnowFood". As well as investigating consumer behaviour and wellbeing, IKnowFood is exploring how farmers in the UK, and businesses across the global food supply chain, can become more resilient in the face of growing uncertainty in markets, regulation and the natural environment."
https://www.sciencedaily.com/releases/2019/02/190205144450.htm
Persistent low body weight in young kids increases risk for anorexia nervosa later
January 31, 2019
Science Daily/University of North Carolina Health Care
A new study has found that a persistent low body mass index (BMI) in children, starting as young as age 2 for boys and 4 for girls, may be a risk factor for the development of anorexia nervosa in adolescence.
In addition, the study, published in the February 2019 issue of the Journal of the American Academy of Child and Adolescent Psychiatry, found that a persistent high BMI in childhood may be a risk factor for later development of bulimia nervosa, binge-eating disorder, and purging disorder. This large population study is based on analysis of data from 1,502 individuals who participated in the Avon Longitudinal Study of Parents and Children in the UK.
"Until now, we have had very little guidance on how to identify children who might be at increased risk for developing eating disorders later in adolescence," said Zeynep Yilmaz, PhD, study first author and an assistant professor of psychiatry and genetics at the UNC Center of Excellence for Eating Disorders in the University of North Carolina School of Medicine. "By looking at growth records of thousands of children across time, we saw early warning profiles that could signal children at risk."
Co-author Cynthia Bulik, PhD, Distinguished Professor of Eating Disorders also from UNC highlights, "Clinically, this means that pediatricians should be alert for children who fall off and stay below the growth curve throughout childhood. This could be an early warning sign of risk for anorexia nervosa. The same holds for children who exceed and remain above the growth curve -- only their risk is increased for the other eating disorders such as bulimia nervosa and binge-eating disorder."
Yilmaz said that although eating disorders are psychiatric in nature, the study highlights the need to also consider metabolic risk factors alongside psychological, sociocultural, and environmental components. "The differences in childhood body weight of adolescents who later developed eating disorders started to emerge at a very early age -- way too early to be caused by social pressures to be thin or dieting. A more likely explanation is that underlying metabolic factors that are driven by genetics, could predispose these individuals to weight dysregulation. This aligns with our other genetic work that has highlighted a metabolic component to anorexia nervosa."
Corresponding author of the study is Nadia Micali, MD, MRCPsych PhD, Full Professor at University of Geneva Faculty of Medicine and Head of Geneva University Hospitals' Division of Child and Adolescent Psychiatry.
"Our results also highlight the multi-factorial composition of eating disorders, as well as the need to develop early detection tools that could be used as part of routine checks by all pediatricians. Indeed, the earlier the problem is identified, the better it can be managed, especially if support is provided to the family as a whole, rather than just the individual," Micali said.
https://www.sciencedaily.com/releases/2019/01/190131143436.htm
Want healthier eating habits? Start with a workout
January 30, 2019
Science Daily/University of Texas at Austin
Researchers have found that formerly sedentary young adults who were instructed to exercise regularly for several weeks started choosing healthier foods without being asked to.
In the latest evidence that it's worth sticking to your health-focused New Year's resolutions, researchers at the University of Texas at Austin have found that exercising regularly is linked to better eating habits.
The new study, published this week in the International Journal of Obesity, looked at 2,680 young adults who were not exercising regularly or dieting. Scientists found that after exercising for several weeks, formerly sedentary study participants were more likely to choose foods like lean meats, fruits and vegetables, while preferences for fried foods, sodas and other unhealthy options decreased.
Participants were instructed not to change their diets in any significant way, but it happened anyway. Although this study did not examine the mechanism at work behind the changes, previous research has found that moderate exercise can reduce a preference for high-fat foods in animals through changes in dopamine levels. Several studies also have shown a relationship between the intensity of exercise and the amount of appetite-regulating hormones in the body.
"The process of becoming physically active can influence dietary behavior," said Molly Bray, corresponding author of the paper and chair of the Nutritional Sciences department at UT Austin and a pediatrics faculty member at Dell Medical School. "One of the reasons that we need to promote exercise is for the healthy habits it can create in other areas. That combination is very powerful."
Bray says what drives food-preference changes when people exercise would probably be consistent across a wide span of ages. The study examined people between the ages of 18 and 35, a period of young adulthood critical for forming healthy habits. Previous studies have found that considerable weight gain occurs during the college years and that being mildly to moderately overweight at age 20-22 increases the risk of obesity later in life.
"Many people in the study didn't know they had this active, healthy person inside them," Bray said. "Some of them thought their size was inevitable. For many of these young people, they are choosing what to eat and when to exercise for the first time in their lives."
The participants in the study were students at the University of Houston and the University of Alabama at Birmingham. Participants who said they exercised less than 30 minutes a week at the beginning of the study started 30-minute aerobic workouts three times a week for 15 weeks, with instructions not to change their diet in any significant way. The exercise sessions consisted of 30 minutes of aerobic exercise at 65-85 percent of the person's age- and gender-specific maximum heart rate, along with a 5-minute warmup and a 5-minute cool down. Participants wore heart-rate monitors and could choose from a variety of exercise types, such as on stationary bikes, treadmills or elliptical machines.
https://www.sciencedaily.com/releases/2019/01/190130112728.htm
Women gain weight when job demands are high
January 25, 2019
Science Daily/University of Gothenburg
Heavy pressures at work seem to predispose women to weight gain, irrespective of whether they have received an academic education. This is shown in a study of more than 3,800 people in Sweden.
"We were able to see that high job demands played a part in women's weight gain, while for men there was no association between high demands and weight gain," says Sofia Klingberg, a researcher in community medicine and public health at Sahlgrenska Academy, University of Gothenburg, and the study's lead author.
The basis for the article, published in the journal International Archives of Occupational and Environmental Health, was the Västerbotten Intervention Program, a Swedish population-based study. Klingberg's study included 3,872 participants in this program.
The women and men in the study were investigated on three occasions over a 20-year period with respect to such variables as body weight and demands and control at work. They were followed either from age 30 to 50 or from 40 to 60.
To estimate the level of job demands, the respondents were asked about their work pace, psychological pressures, whether there was enough time for their duties and how often the demands made were contradictory.
The questions about control at work covered such matters as how often they learned something new; whether the job called for imagination or advanced skills; and whether the respondent was personally able to choose what to do and how to do it.
The results show that the respondents with a low degree of control in their work more frequently gained considerable weight, defined as a weight gain of 10 percent or more, in the course of the study. This applied to women and men alike.
On the other hand, long-term exposure to high job demands played a part only for women. In just over half of the women who had been subjected to high demands, a major increase in weight took place over the 20 years. This gain in weight was some 20 percent higher than in women subject to low job demands.
"When it came to the level of demands at work, only the women were affected. We haven't investigated the underlying causes, but it may conceivably be about a combination of job demands and the greater responsibility for the home that women often assume. This may make it difficult to find time to exercise and live a healthy life," Klingberg says.
Having had or not had an academic education does not explain the associations in the study. Neither do quality of diet or other lifestyle factors. However, the information about dietary intake comes from the respondents themselves, with a certain risk of incorrect reporting.
At the same time, given the problems associated with work-related stress, the study is relevant in terms of public health. The researchers think identification of groups who are susceptible to stress and efforts to reduce work-related stress would likely achieve a decrease not only in weight gain but also in the incidence of ill health, including cardiovascular disease and diabetes.
https://www.sciencedaily.com/releases/2019/01/190125172950.htm
Want healthier eating habits? Start with a workout
January 30, 2019
Science Daily/University of Texas at Austin
Researchers have found that formerly sedentary young adults who were instructed to exercise regularly for several weeks started choosing healthier foods without being asked to.
In the latest evidence that it's worth sticking to your health-focused New Year's resolutions, researchers at the University of Texas at Austin have found that exercising regularly is linked to better eating habits.
The new study, published this week in the International Journal of Obesity, looked at 2,680 young adults who were not exercising regularly or dieting. Scientists found that after exercising for several weeks, formerly sedentary study participants were more likely to choose foods like lean meats, fruits and vegetables, while preferences for fried foods, sodas and other unhealthy options decreased.
Participants were instructed not to change their diets in any significant way, but it happened anyway. Although this study did not examine the mechanism at work behind the changes, previous research has found that moderate exercise can reduce a preference for high-fat foods in animals through changes in dopamine levels. Several studies also have shown a relationship between the intensity of exercise and the amount of appetite-regulating hormones in the body.
"The process of becoming physically active can influence dietary behavior," said Molly Bray, corresponding author of the paper and chair of the Nutritional Sciences department at UT Austin and a pediatrics faculty member at Dell Medical School. "One of the reasons that we need to promote exercise is for the healthy habits it can create in other areas. That combination is very powerful."
Bray says what drives food-preference changes when people exercise would probably be consistent across a wide span of ages. The study examined people between the ages of 18 and 35, a period of young adulthood critical for forming healthy habits. Previous studies have found that considerable weight gain occurs during the college years and that being mildly to moderately overweight at age 20-22 increases the risk of obesity later in life.
"Many people in the study didn't know they had this active, healthy person inside them," Bray said. "Some of them thought their size was inevitable. For many of these young people, they are choosing what to eat and when to exercise for the first time in their lives."
The participants in the study were students at the University of Houston and the University of Alabama at Birmingham. Participants who said they exercised less than 30 minutes a week at the beginning of the study started 30-minute aerobic workouts three times a week for 15 weeks, with instructions not to change their diet in any significant way. The exercise sessions consisted of 30 minutes of aerobic exercise at 65-85 percent of the person's age- and gender-specific maximum heart rate, along with a 5-minute warmup and a 5-minute cool down. Participants wore heart-rate monitors and could choose from a variety of exercise types, such as on stationary bikes, treadmills or elliptical machines.
https://www.sciencedaily.com/releases/2019/01/190130112728.htm
Not all saturated fats are equal when it comes to heart health
Cardiovascular risk of diets rich in saturated fats found in meats and the benefits of plant-based and dairy alternatives
January 28, 2019
Science Daily/Elsevier
The type of saturated fats we eat can affect our risk of a heart attack, according to a study published in the International Journal of Cardiology. People whose diets contain relatively little palmitic and stearic acid -- saturated fats composed of 16 or more carbon atoms (longer-chain saturated fats) that are typically found in meats -- and eat plant-based proteins instead have decreased chances of myocardial infarction. Moreover, individuals who eat more saturated fats with 14 or fewer carbon atoms (shorter-chain saturated fats) that are typically found in dairy products have lower risk of myocardial infarction.
"Our analysis of the diets of large groups of individuals in two countries over time shows that the type of saturated fats we consume could affect our cardiovascular heath," explained lead investigator Ivonne Sluijs, PhD, Julius Center for Health Sciences and Primary Care, University Medical Center Utrecht, Utrecht University, Utrecht, Netherlands.
The study investigated whether saturated fats with chains varying in length from 4 to 18 carbon atoms are associated with the risk of developing a myocardial infarction. Data from approximately 75,000 people in the UK and Denmark were analyzed. Of these two groups, nearly 3,500 people experienced myocardial infarction in the period between the study's initial outreach and follow-up 13 years later (in Denmark) and 18 years later (in the UK).
"We found that eating relatively little of the longer chained saturated fatty acids and consuming plant-based proteins instead was associated with a lowered risk. Substitution of those saturated fats with other energy sources such as carbohydrates did not affect the risk to develop myocardial infarction," said Dr. Sluijs. Although diets vary by nationality and other factors, the most frequently consumed saturated fat is palmitic acid, with 16 carbon atoms, followed by stearic acid, with 18 carbon atoms, both of which are found in meat products. Consumption of saturated fats that have shorter carbon atom chains and are present in dairy products is less prevalent.
Since the 1960s, when diets high in saturated fat were linked to elevated "bad" LDL cholesterol and coronary heart disease, dietary guidelines recommended restricting saturated fatty acids across the board. In recent years, research studies have raised some questions about what was considered established evidence. Inconsistent findings have pointed to the possibility that different types of saturated fats have different effects on cholesterol levels and the development of coronary heart disease. Despite the fact that their study's findings support this hypothesis, Dr. Sluijs and her fellow investigators recommend proceeding with caution before changing dietary guidelines:
"Our study only allowed us to draw conclusions on the level of associations between saturated fatty acids and the development of myocardial infarction. We do not know whether those fatty acids are actually the cause of differences between the occurrences of myocardial infarction we observed. To further explore this, we need experiments in which the consumption of saturated fatty acids is more controlled and, for instance, compared with consumption of unsaturated fatty acids," she noted.
"The study is applaudable for its large size, prospective cohort study design, and detailed assessment of diet and lifestyle factors. In addition, it is among the few studies that specifically examined individual saturated fatty acids in relation to coronary heart disease risk and compared with different macronutrients," commented Jun Li, MD, PhD, and Qi Sun, MD, ScD, both at the Harvard T.H. Chan School of Public Health, Boston, MA, USA, in an accompanying editorial. They also noted a few limitations of the study and thus called for cautious interpretation of the overall null results for the primary saturated fatty acids.
Dr. Li and Dr. Sun advise that shifts in fat intake should align with the recommended healthy dietary patterns, which emphasize limited intakes of red and processed meat and added sugars, lower salt intake, replacement of refined grains with whole grains, and higher consumption of fruits and vegetables.
https://www.sciencedaily.com/releases/2019/01/190128105230.htm
Excessive body fat around the middle linked to smaller brain size
January 9, 2019
Science Daily/American Academy of Neurology
Carrying extra body fat, especially around the middle, may be linked to brain shrinkage, according to new research. For the study, researchers determined obesity by measuring body mass index (BMI) and waist-to-hip ratio in study participants and found those with higher ratios of both measures had the lowest brain volume.
BMI is a weight-to-height ratio. It is determined by dividing a person's weight by the square of their height. People with a BMI above 30.0 are considered obese. Waist-to-hip ratio is determined by dividing waist circumference by hip circumference. People with bigger bellies compared to their hips have higher ratios. Men above 0.90 and women above 0.85 are considered to be centrally obese.
"Existing research has linked brain shrinkage to memory decline and a higher risk of dementia, but research on whether extra body fat is protective or detrimental to brain size has been inconclusive," said study author Mark Hamer, PhD, of Loughborough University in Leicestershire, England. "Our research looked at a large group of people and found obesity, specifically around the middle, may be linked with brain shrinkage."
The study looked at 9,652 people with an average age of 55. Of that group, 19 percent were determined to be obese. Researchers measured BMI, waist-to-hip ratio and overall body fat and surveyed participants about their health. Researchers then used magnetic resonance imaging to determine brain volumes for white and gray brain matter and volumes in the various regions of the brain.
Gray matter contains most of the brain's nerve cells and includes brain regions involved in self-control, muscle control and sensory perception. White matter contains nerve fiber bundles that connect various regions of the brain.
After adjusting for other factors that may affect brain volume, such as age, physical activity, smoking and high blood pressure, researchers found that while a high BMI alone was linked to slightly lower brain volumes, those with high BMI and waist-to-hip ratios had lower gray matter brain volumes than participants who did not have a high waist-to-hip ratio. Specifically, researchers found that 1,291 people who had a high BMI and a high waist-to-hip ratio had the lowest average gray matter brain volume of 786 cubic centimeters, compared to 3,025 people of healthy weight who had an average gray matter brain volume of 798 cubic centimeters and 514 people with a high BMI but without high waist-to-hip ratio who had an average gray matter brain volume of 793 cubic centimeters. They found no significant differences in white matter brain volume.
"While our study found obesity, especially around the middle, was associated with lower gray matter brain volumes, it's unclear if abnormalities in brain structure lead to obesity or if obesity leads to these changes in the brain," said Hamer. "We also found links between obesity and shrinkage in specific regions of the brain. This will need further research but it may be possible that someday regularly measuring BMI and waist-to-hip ratio may help determine brain health."
A limitation of the study was that only 5 percent of those invited to participate in the study took part, and those who participated tended to be healthier than those who did not, so the results may not reflect the population as a whole.
https://www.sciencedaily.com/releases/2019/01/190109164233.htm
Personality type could shape attitudes toward body weight of others
January 15, 2019
Science Daily/Florida State University
Researchers found that personality traits have significant bearing on a person's attitudes toward obesity, their implicit theories of weight and their willingness to engage in derisive fat talk or weight discrimination.
Studies show there is a major link between personality traits and personal body image, but the relationship between personality and attitudes toward others' bodies has gone largely unexplored.
Now, Florida State University researchers suggest that the specific alchemy of an individual's personality -- their distinct blend of conscientiousness, agreeableness, openness, neuroticism and extraversion -- is directly related to their beliefs about others' bodies and the ways those beliefs are expressed in social interactions.
In a study published in the journal Personality and Individual Differences, researchers found that the relative prominence of these five personality traits, which together constitute the Five Factor model of personality, has a significant bearing on a person's attitudes toward obesity, their implicit theories of weight and their willingness to engage in derisive fat talk or weight discrimination.
"Individuals who are higher in neuroticism hold more negative attitudes about obesity, they show more phobia toward weight, they talk more negatively about their body to their friends and around their children, and they are more likely to perceive weight discrimination," said study co-author Angelina Sutin, associate professor in FSU's College of Medicine.
The scientific literature has long suggested a strong connection between personality and body weight. People who score high in conscientiousness, for example, tend to weigh less and have lower long-term risk of obesity, whereas people higher in neuroticism tend to harbor negative emotions about their bodies.
While these connections present a compelling case for the power of personality in predicting a person's body weight or coloring a person's body image, Sutin and her team were interested in broadening this line of inquiry beyond the individual. They wanted to learn more about how personality may be modulating body weight experiences in the social realm.
"There is a social dimension to body weight," Sutin said. "People have attitudes about body weight and what contributes to obesity. People also often vocalize their fears about how they look and what they need to do to lose weight. We wanted to know whether personality contributes to this social experience."
Sutin and her team interviewed 3,099 women with children using a series of carefully crafted surveys that allowed researchers to map respondents' attitudes and behaviors onto their individual Five Factor personality profiles. Their results were largely in line with expectation: higher neuroticism foretold more negative attitudes, and higher conscientiousness generally aligned with more positive attitudes and behaviors.
One finding, though, surprised Sutin and her team. Their surveys pointed to a significant association between conscientiousness and greater fat phobia.
"One aspect of conscientiousness is following the norms of society," Sutin said. "Even though two-thirds of the U.S. population is overweight or obese, there are strong social ideals for health and fitness -- even if, on average, we do not meet these ideals."
People high in conscientiousness -- already preconditioned to follow rules and hold to prevailing social beliefs -- may internalize these ideals, Sutin said. Eventually, that may result in expressions of phobia toward obesity.
"Their endorsement of obesity stereotypes may be consistent with their need to fit with beliefs held by society more broadly," Sutin and her co-author, FSU College of Medicine Associate Professor Antonio Terracciano, wrote in their study.
While these results need to be replicated to confirm their validity beyond this specific cohort of mothers, Sutin said both individuals and society would benefit from renewed scrutiny on attitudes toward others' bodies.
"Attitudes have broad-reaching consequences -- for how the individual feels and responds to their body, for shaping children's attitudes toward their own bodies and the bodies of those around them, and for policy," she said. "If people hold negative attitudes toward obesity, that could shape the way that policies are made and implemented and perpetuate stigma toward obesity rather than constructive ways to address it."
This research was supported by the National Institute on Aging of the National Institutes of Health.
https://www.sciencedaily.com/releases/2019/01/190115124436.htm
Slim people have a genetic advantage when it comes to maintaining their weight
January 24, 2019
Science Daily/University of Cambridge
In the largest study of its kind to date, researchers have looked at why some people manage to stay thin while others gain weight easily. They have found that the genetic dice are loaded in favor of thin people and against those at the obese end of the spectrum.
More than six in ten adults in the UK are overweight, and one in four adults is obese. By age five, almost one in four children is either overweight or obese. Excess weight increases the risk of related health problems including type 2 diabetes and heart disease.
While it is well known that changes in our environment, such as easy access to high calorie foods and sedentary lifestyles, have driven the rise in obesity in recent years, there is considerable individual variation in weight within a population that shares the same environment. Some people seem able to eat what they like and remain thin. This has led some people to characterise overweight people as lazy or lacking willpower.
With support from Wellcome and the European Research Council, a team led by Professor Sadaf Farooqi at the Wellcome-MRC Institute of Metabolic Science, University of Cambridge, established the Study Into Lean and Thin Subjects -- STILTS -- to examine why and how some people find it easier to stay thin than others. Studies of twins have shown that variation in body weight is largely influenced by our genes. To date studies have overwhelmingly focused on people who are overweight. Hundreds of genes have been found that increase the chance of a person being overweight and in some people faulty genes can cause severe obesity from a young age.
Professor Sadaf Farooqi's team were able to recruit 2,000 people who were thin (defined as a body mass index (BMI) of less than 18 kg/m2) but healthy, with no medical conditions or eating disorders. They worked with general practices across the UK, taking saliva samples to enable DNA analysis and asking participants to answer questions about their general health and lifestyles. It is thought to be the only cohort of its kind in the world and the researchers say that the UK's National Institute for Health Research -- the National Health Service's research infrastructure -- strongly enabled and supported their research.
In a study published today in the journal PLOS Genetics, Professor Farooqi's team collaborated with Dr Inês Barroso's team at the Wellcome Sanger Institute to compare the DNA of some 14,000 people -1,622 thin volunteers from the STILTS cohort, 1,985 severely obese people and a further 10,433 normal weight controls.
Our DNA comprises of a sequence of molecules known as base pairs, represented by the letters A, C, G and T. Strings of these base pairs form genetic regions (which include or make up our genes). Our genes provide the code for how our body functions and changes in the spelling -- for example, a C in place of an A -- can have subtle or sometimes dramatic changes on features such as hair colour and eye colour but also on a person's weight.
The team found several common genetic variants already identified as playing a role in obesity. In addition, they found new genetic regions involved in severe obesity and some involved in healthy thinness.
To see what impact these genes had on an individual's weight, the researchers added up the contribution of the different genetic variants to calculate a genetic risk score.
"As anticipated, we found that obese people had a higher genetic risk score than normal weight people, which contributes to their risk of being overweight. The genetic dice are loaded against them," explains Dr Barroso.
Importantly, the team also showed that thin people, had a much lower genetic risk score -- they had fewer genetic variants that we know increase a person's chances of being overweight.
"This research shows for the first time that healthy thin people are generally thin because they have a lower burden of genes that increase a person's chances of being overweight and not because they are morally superior, as some people like to suggest," says Professor Farooqi. "It's easy to rush to judgement and criticise people for their weight, but the science shows that things are far more complex. We have far less control over our weight than we might wish to think."
Three out of four people (74%) in the STILTS cohort had a family history of being thin and healthy and the team found some genetic changes that were significantly more common in thin people, which they say may allow them to pinpoint new genes and biological mechanisms that help people stay thin.
"We already know that people can be thin for different reasons" says Professor Farooqi. "Some people are just not that interested in food whereas others can eat what they like, but never put on weight. If we can find the genes that prevent them from putting on weight, we may be able to target those genes to find new weight loss strategies and help people who do not have this advantage."
https://www.sciencedaily.com/releases/2019/01/190124141538.htm