Benefits of gastric bypass surgery linked to changes in sweet taste preference
Worldwide, the number of patients struggling with obesity is rapidly increasing in both adults and children. Diet and exercise are the mainstays of treatment for obesity, but have limited effectiveness. While bariatric surgery can produce sustained and significant weight loss for most patients, not all patients experience similar benefits. The reasons for this variation are unknown, but researchers at the Johns Hopkins University School of Medicine believe that part of the answer may lie in how taste preferences are altered by weight loss surgery. Kimberley Steele MD PhD, Principal Investigator and Director of Bariatric Research at Hopkins, was inspired to investigate this phenomenon after observing that her gastric bypass patients had a heightened sensitivity to sweet foods after surgery. Dr. Steele and her team of neuroscientists and imaging specialists hypothesized that the factors responsible for variation in weight loss following bariatric surgery may lie not just in the gut but also in the brain.
Dr. Steele’s team studied taste preferences for sugars and fats in patients prior to surgery and up to 3 months after Roux-en-Y gastric bypass (RYGB) or vertical sleeve gastrectomy (VSG). While both RYGB and VSG procedures reduce the size of the stomach, RYGB also reroutes the progression of food through the intestines. Thus it alters many of the gut responses that would usually be triggered during digestion. Their preliminary data show that all patients experienced a decrease in their liking of sweet taste, but a more pronounced effect was observed with RYGB. No changes in fat preference were observed in either group. “These preliminary data suggest that the changes in sweet taste preference in individuals who had RYGB may be driven by alterations in the reward value of food induced by the anatomical and/or metabolic changes that occur with RYGB.” says Dr. Kimberly Smith, a postdoctoral fellow and co-investigator on the team.
A better understanding of what drives changes in diet selection following bariatric surgery may allow clinicians to predict which patients will respond best to different types of surgery, and may provide insight into the mechanisms responsible for overeating in the obese, of potential importance to the development of surgical and non-surgical approaches to the treatment of obesity.
Kimberley Steele, PhD
Replacing a palatable high-fat diet with low fat food causes withdrawal-like symptoms in mice
Researchers have found that mice fed a palatable high-fat diet experience stress responses that resemble drug withdrawal when their food is switched to a low-fat diet. A study conducted by Dr. Steve Fordahl, currently at the University of North Carolina at Greensboro, and Dr. Sara Jones at Wake Forest School of Medicine, identified brain changes in the dopamine neurotransmitter system caused by stress when the palatable diet was removed. The diet switch triggered a physiological stress response that supressed brain dopamine, which in turn promoted binge-eating when the palatable diet was re-introduced days later. Their research will be presented this week at the Society for the Study of Ingestive Behavior’s (SSIB) annual meeting in Montreal Quebec, among a lineup of international researchers that examine eating and drinking behaviors.
Changing eating habits can be very difficult. People commonly over-restrict while dieting, which may not be the best strategy for sustained weight loss. Sometimes healthcare professionals urge changes in eating habits to avoid pressing health consequences, like cardiovascular disease or advanced diabetes. A stark dietary shift from comfort foods, often high in saturated fat, for less desirable healthy options can be challenging. This new research identifies how an individual’s physiological stress response to new eating patterns causes quick relapse into old habits, despite their best intentions. The study by Dr. Fordahl and Dr. Jones shows that, in mice, dietary relapse is enhanced by stress-related molecules that change dopamine levels in brain regions that process reward. Dopamine helps attribute the perceived value, or rewarding characteristics of food, and changes in the dopamine system observed in the study were similar to what drug- and alcohol-dependent people experience when going through withdrawal.
In the study, mice were fed a high-fat diet, then abruptly switched to a low-fat alternative. The investigators observed voluntary food restriction of the new diet, persisting several days after the change. They also identified a reduction in dopamine caused by enhanced sensitivity to activation of receptors for the stress signals, corticotrophin releasing factor (CRF) and the dynorphin/kappa opioid receptor (KOR) system, on dopamine neurons. When the palatable high-fat diet was returned, mice displayed binge-like feeding, eating substantially more high-fat food than before the dietary switch. Interestingly, when the investigators blocked CRF and KOR activation, the dopamine system normalized, and mice did not binge when high-fat food was returned.
“Our findings suggest that stress caused by food restriction, commonly observed with crash dieting, can prime the dopamine system in a way that promotes over-indulgence of palatable or ‘comfort’ foods, when the opportunity arises,” said Dr. Steve Fordahl. The research team finds that dietary fat has a “particularly strong impact on how the dopamine system responds to rewards,” and collaborative work between Dr. Jones and Dr. Fordahl to further characterize this relationship is underway.
Research: Replacing a high fat diet with chow causes a withdrawal-like stress response at dopamine terminals in mice.
- Steve C. Fordahl, Department of Nutrition, UNC-Greensboro, Greensboro, NC, USA.
- Sara R. Jones, Department of Physiology and Pharmacology, Wake Forest School of Medicine, Winston-Salem, NC, USA.
Dr. Steve Fordahl
Restaurant placemats can help promote healthy eating among children
July 17, 2017 BUFFALO, N.Y. — Placemats can be used to encourage children to eat healthier food in restaurants, according to a new study by the University at Buffalo and Independent Health Foundation.
Researchers used the dining accessory, known mostly for quirky games and local business advertisements, as a tool to promote healthier menu options in fun and engaging ways.
While hot dogs and chicken tenders remained the meal of choice for most of the 4 to 8 year olds who participated in the study, the placemats helped convince some children to choose healthier options such as turkey on whole wheat bread (Gobble-Me-Up Turkey Sandwich) or a peanut butter and banana sandwich (The Nutty Monkey). Children exposed to the placemats prior to ordering were more likely to choose healthier food options compared to a control group.
“Many families eat food from restaurants on a regular basis, with research suggesting that children tend to consume less healthy foods in these settings compared to home,” said the study’s lead author Stephanie Anzman-Frasca. “In this study, our goal was to feature healthier children’s meal options prominently to see whether this could affect children’s orders and intake.”
Anzman-Frasca, PhD, assistant professor in the Department of Pediatrics in the Jacobs School of Medicine and Biomedical Sciences at University of Buffalo, presented the findings this week at the Society for the Study of Ingestive Behavior conference in Montreal.
Anzman-Frasca and fellow researchers recruited 58 children (and their parents) within one location of Anderson’s Frozen Custard, a quick-service restaurant chain in the Buffalo Niagara region, in the fall of 2016. The families were each given a voucher to return to the restaurant once during a randomly assigned two-week period. Upon returning to the restaurant, half of the children were given a placemat promoting two healthier children’s meals as “Meals of the Day”. The meals were listed alongside fun names and images, as well as activities such as a word search. The rest of the children were in a control group and received no placemats.
Children who were exposed to the placemats before ordering were significantly more likely to order healthier food options. Eighteen percent of the children in the placemat group ordered one of the featured healthier entrées, compared to 7 percent in the control group.
The groups did not differ in the likelihood of ordering dessert or healthier beverages.
The children who ordered the healthier entrées consumed less saturated fat across the total meal compared to those who did not.
“These results suggest that restaurants can help promote healthier eating among children by featuring healthier items more prominently on materials that are viewed prior to ordering,” said Anzman-Frasca. “Making healthy options appealing and easy to choose offers the potential to increase children’s acceptance of them in restaurants. At the same time, there is room for future efforts to build on the current results, aiming to normalize healthy options in restaurants further and nudge even more children toward healthier choices.”
“The effect of a liking norm message on the consumption of fruit, vegetables and energy dense snack foods.”
- Abbey Braun, University at Buffalo, NY, USA
- Sarah Ehrenberg, University at Buffalo, NY, USA
- Lucia Leone, University at Buffalo, NY, USA
- Anita Singh, University at Buffalo, NY, USA
- Sara Tauriello, University at Buffalo, NY, USA
- Leonard Epstein, University at Buffalo, NY, USA
- April Gampp, Independent Health Foundation, NY, USA
Cory Nealon, University at Buffalo
New combination of anti-obesity drugs may have beneficial effects
Research conducted in the Perelman School of Medicine at the University of Pennsylvania has revealed that a unique combination of hormone-based drugs can produce enhanced weight loss in laboratory tests with obese animals. The research is to be presented this week at the Annual Meeting of the Society for the Study of Ingestive Behavior (SSIB), the foremost society for research into all aspects of eating and drinking behavior.
“Imagine a drug regimen where an obese person would cycle between different drug therapies over the course of a month to achieve a greater degree of body weight loss compared to the effects achieved with either a single drug or the continuous combination of drugs,” said senior author Dr. Matthew Hayes. His team studied the combination of two different drug classes that target different hormones: amylin and glucagon-like peptide-1 (GLP-1). They found that combined treatments acted synergistically to suppress feeding and body weight. They also discovered that the weight loss effects of chronic amylin- and GLP-1-based combination therapies could be enhanced when obese lab animals are cycled through their drug treatments. “The idea of drug-cycling is nothing new,” says lead author Kieran Koch-Laskowski. “Millions of women on birth control pills, for example, already take daily pills that cycle between drug and placebo throughout the month,” she goes on to say.
Perhaps the most exciting finding of the current data coming out of Penn is the fact that the research finds these enhanced weight loss effects with a combination of drugs that are either already FDA approved or in clinical trials for metabolic diseases, “making the translational impact of our work extremely timely and highly clinically relevant!” says Hayes. The authors are now finalizing their research to demonstrate mechanically how these two hormonal systems interact to achieve greater weight loss in the hopes of fast-tracking their findings to new clinical treatments for obesity.
Senior Author: Matthew R. Hayes, Department of Psychiatry, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA.
- Kieran Koch-Laskowski, Department of Psychiatry, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA.
- Lauren E. McGrath, Department of Psychiatry, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA.
- Evan Shaulson, Department of Psychiatry, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA.
Matthew R. Hayes, Ph.D.
Does exercise facilitate body weight control? The answer may depend on sex.
Healthcare practitioners regularly prescribe diet and exercise as a method for patients to lose weight. But exercise might not be equally effective in males and females, according to new research conducted at the University of Colorado, Anschutz Medical Campus.
In a study conducted in rats, graduate student Rebecca Foright fed both male and female rats a high fat diet and then trained half of them to run on a treadmill. After a total of 10 weeks, there was a remarkable sex difference in response to the exercise training. Male rats who exercised ate less food and gained less weight than sedentary males. Exercising female rats did not reduce their food intake. At the end of the study they weighed the same as sedentary females. When this study was repeated in males fed a low fat diet, the research team found that the impact of exercise on body weight was evident even sooner than in the high fat diet fed male rats.
These findings will be presented this week at the Annual Meeting of the Society for the Study of Ingestive Behavior, the leading scientific society for research into all aspects of eating and drinking behavior.
Other researchers have reported that a single bout of exercise leads to an increase in interleukin-6 (IL-6) in the hypothalamus of male rodents. The hypothalamus is a brain area playing a key role in monitoring signals from the body to properly regulate feeing behavior. IL-6 is produced by muscle cells during acute bouts of strenuous exercise, and it may also be produced in the brain with exercise. Studies have shown that IL-6 could mediate the beneficial effects of exercise on body weight regulation, by enhancing the brain’s response to hormones that suppress food intake.
Surprisingly, this story of IL-6 and acute exercise does not readily translate to the exercise-trained condition. When researchers from the University of Colorado measured IL-6 in their studies, they found that exercise-trained male rats had decreased hypothalamic IL-6, while the exercised females had increased IL-6. They believe that chronic exercise, unlike a single bout of exercise, may be imparting the sex specific differences in body weight control through differential effects on hypothalamic inflammation, rather than by acutely altering local concentrations of IL-6.
Despite an increased prevalence of obesity in women and physiological differences between males and females in the hormonal signals and brain processes that influence appetite, the vast majority of mechanistic studies on obesity and treatment are performed in male animals. Foright says, “I hope that this research inspires other investigators to examine a female-specific response in their animal models. It is unacceptable to simply assume that females will respond to interventions in the same manner as males.” She and her research team will continue to study female physiology to understand these sex-specific differences of exercise training.
Research: Sex-specific response to exercise training in rats fed a high fat diet.
Authors: RM FORIGHT1, GC JOHNSON1, VD SHERK1, MR HAYES2, PS MACLEAN1
Affiliations:1University of Colorado Denver AMC, Denver, CO, United States
2Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA, United States
Rebecca Foright, MS
Estrogen in the brain prevents obesity and glucose intolerance during menopause in lab animal study
Researchers at the University of Cincinnati (UC) have found that adding estrogen in the brain may improve health in obese females after menopause.
The study conducted by Christina Estrada, a doctoral candidate in the UC psychology graduate program in the laboratory of Matia Solomon, PhD, an Associate Professor in the UC Department of Psychiatry and Behavioral Neuroscience, used surgically-induced menopause to cause obesity in rats and identified brain areas that benefit from estrogen replacement. The findings will be presented this week at the annual meeting of the Society for the Study of Ingestive Behavior (SSIB), a leading society for research in eating and drinking behavior.
“We know as women age and enter into menopause, they tend to gain body weight and body fat, particularly in the abdominal or ‘belly’ area. Excess abdominal fat greatly increases risk for cardio-metabolic diseases,” says Solomon. “While there are likely many factors that are associated with these risks in menopausal women, estrogen loss is associated with body weight and fat gain during menopause. In fact, estrogen treatment can offset this weight gain in many women.”
The medial amygdala (MeA) is a region of the brain that helps regulate body weight and contains an abundance of estrogen receptors (molecules that respond to estrogen). The researchers used an experimental model in rats, which involves removing the ovaries to mimic the hormonal changes of menopause. They targeted estrogen replacement directly in the MeA and found that it prevented weight and abdominal fat gain and improved glucose tolerance, compared to rats in a placebo group. This suggests that the MeA is important in the metabolic health of menopausal females and may be a useful target for treatment.
“Obesity is a national epidemic and women are becoming obese at younger ages. Given the beneficial effects of estrogen on metabolic health, we were interested in determining the consequences of obesity on estrogen-related endpoints in female rats, akin to younger, premenopausal women,” says Estrada. A separate group of female rats with intact ovaries were placed on a high-fat diet. Relative to their lean counterparts, obese females had increased blood estrogen levels, irregular reproductive cycles and altered estrogen receptor activity in several brain regions regulating metabolic function.
These findings suggest obesity may dampen the metabolically beneficial effects of estrogen in the body and in the brain in females.
“These findings are particularly important because we know very little about the impact of obesity on brain function in women,” Estrada says, adding that the research team believes understanding how the brain and body work together to regulate metabolic health offers a more holistic perspective of how to tackle obesity prevention in women. The research team is focused on understanding how obesity impacts brain health in females and whether these changes are temporary or permanent.
Matia B. Solomon, Ph.D.
Department of Psychiatry & Behavioral Neuroscience, University of Cincinnati
Obese and overweight less likely to consider next meal when making portion size decisions.
University of Bristol researchers have found that people with obesity tend to ignore how long it will be until the next meal when choosing how much to eat. In a study designed see if people consider the time interval between two meals when selecting portion sizes, the researchers found that lean people generally do. However, obese people tend to discount that information. The findings will be presented this week at the 2017 Annual Meeting of the Society for the Study of Ingestive Behavior (SSIB), the leading scientific society for research into all aspects of eating and drinking behavior.
Obesity has previously been linked to differences in “delay discounting” – the tendency to treat something as less significant based on how far in the future it will occur. Delay discounting is a facet of impulsivity, encouraging decisions in the moment that disregard future rewards or consequences. Typically psychologists study how discounting works in tasks using money. In this study, for the first time, the Bristol researchers assessed how people with obesity discount information about future meal timings.
“Meal timings and future planning are an important area of research in obesity. These findings are exciting because they are the first to demonstrate that discounting operates in planning from one meal to the next and that people with obesity might not be factoring that in to their choices,” said lead author Annie Zimmerman, a doctoral student at the University of Bristol. “Our results are consistent with the idea that overeating is promoted by feeling in the moment, disregarding future consequences of decisions. This novel finding might help to explain why being overweight is associated with irregular meal timings. Potentially there could be targeted interventions for obesity to promote future thinking in meal planning.”
In the study, participants completed a series of computerized tasks, which included selecting lunch portion sizes after being told how long after lunch the next meal would be (ranging up to 8 hours later). The researchers found that individuals with a high BMI were less influenced by information about the inter-meal interval when making portion size decisions. Additionally, participants completed a monetary delay discounting task. There was no interaction between the monetary delay discounting task and the inter-meal interval task, although both independently predicted BMI. This suggests that these factors work in parallel, but tap into separate traits related to obesity.
“It is particularly interesting that monetary discounting was not related to sensitivity to future meal timings. The literature is beginning to differentiate between discounting of food and money – our findings are consistent with the idea that there temporal discounting works differently for different reward types. Our results highlight the need to distinguish between long-term monetary discounting and shorter-term discounting between meals. To fully understand the role of dietary discounting in eating behaviours and the links to obesity we need to develop a multifaceted model of discounting,” explained Zimmerman.
This research was supported by the European Union Seventh Framework Programme Nudge-it project (FP7/2007–2013).
Research: Obese and overweight, relative to lean, individuals discount information about the inter-meal interval when selecting portion size
Lead Author: Annie Zimmerman, University of Bristol, Priory Road, Bristol, UK
Co-Author: Alice Mason, Peter Rogers, Jeff Brunstrom