Posts Tagged ‘research’
Friday, July 8th, 2011
Despite fewer super-sized meals, American’s waistlines continue to expand, according to a recent study funded by the National Institutes of Health.
According to University of North Carolina at Chapel Hill researchers who conducted the study and examined surveys of daily eating habits over a 30-year period, the number of daily meals and snacks consumed by U.S. adults rose to 4.8 in 2006 from 3.8 in 1977.
Many health professionals say that frequent eating in small doses revs up the metabolism and controls hunger, and is a healthier way of eating than three big meals. However, much consideration must also be given to what and how much you eat over the course of the day, not just how often you eat.
Case in point: the analysis also found that although the size of meal portions has stabilized in recent years, the number of total calories consumed is rising. By 2006, the end of the period studied, Americans were consuming 570 more calories per day than they did in the late 1970s. A chief culprit behind the calorie gain: Americans now consume 220 more calories daily from sugar-sweetened soft drinks than they did in the 1960s, the study found.
So it’s okay to switch to diet soda, right? Not so fast. Two new studies presented recently at the American Diabetes Association’s (ADA) Scientific Sessions have linked drinking diet soda to weight gain and that the artificial sweeteners in them could potentially contribute Type 2 diabetes.
In one study, researchers from the School of Medicine at The University of Texas Health Science Center San Antonio, looked at aggregate data from 474 older adults in the San Antonio Longitudinal Study of Aging, or SALSA. At the time of enrollment and at three follow-up exams thereafter, all participants reported their diet soda intake and were measured for height, weight and waist circumference. The researchers wanted to track any association between diet soda drinking and body fat over time.
People who said they drank two or more diet sodas a day experienced waist size increases that were six times greater than those of people who didn’t drink diet soda, according to researchers from the University of Texas Health Science Center at San Antonio. Researchers said their results were adjusted for other contributing factors like diabetes status, leisure-time physical activity level and age.
The data didn’t say why diet sodas might play a role in weight gain, but previous research suggests it has to do with the idea that the brain is wired to expect a big load of calories when foods taste sweet or fatty, but because diet foods fail to deliver, it throws the brain out of whack. Studies in animals suggest that artificial sweetener consumption may lead to even more eating and weight gain, perhaps in part because it triggers the body to start storing more calories as fat.
A second study that found the sweetener aspartame raised blood sugar levels in diabetes-prone mice. The researchers, also from the School of Medicine at The University of Texas Health Science Center San Antonio, fed aspartame, a calorie-free sweetener used in some diet sodas, to diabetes-prone mice. One group of mice ate chow to which both aspartame and corn oil were added; another other group ate chow with only corn oil added. After three months, the mice that ate aspartame showed elevated blood sugar levels. The findings aren’t directly translatable to humans, but may still be meaningful. Maybe it’s time to switch to carbonated water.
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Tags: blood, diet, research, soda, study, sugar, weight
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Monday, June 20th, 2011
We’ve all experienced food cravings, the feeling that we don’t just want to eat something — we want something very specific. Researchers at Tufts University found that the types of foods people crave are individual, but generally speaking, people crave foods that are high in calories. For a better understanding of food cravings, it’s important to understand what influences our cravings and what we can do to control them.
In the May 2010 issue of Current Directions in Psychological Science, a journal of the Association of Psychological Science, psychologists Eva Kemps and Marika Tiggemann of Flinders University, Australia, reviewed the latest research on food cravings to answer one question: Why do we get intense desires to eat certain foods? They found some studies to suggest that the mental imagery of food (the vivid images we get when we crave) hold the key. In fact, one study found that the strength of an individuals craving was correlated with how vividly they imagined the food.
If this is the case, then the media may play a large role in why and what we crave. Considering that children in the U.S. are exposed to approximately 5,500 food commercials from television each year – 98% of which are promoting products that are high in salt, fat, and sugar – it’s no surprise that in a study published in Health Psychology by Dr. Jennifer Harris and colleagues at Yale University, researchers found that children and adults who watched advertisements for snack foods ate significantly more than those who were not exposed to ads (children ate 45% more and adults ate 33% more).
Aside from the media, what we crave may also be a preference we are born with. What our mothers ate during their pregnancy has a big impact on our food preferences. Julie Mennella, a biologist at the Monell Chemical Sciences Center, found that as babies grow in the womb, they begin to ingest up to a liter of amniotic fluid a day, leading to exposure to flavors that he or she will prefer as an infant. For her study, Mennella gave one group of subjects carrot juice four times a week and switched to water when breastfeeding, gave the second group water during pregnancy and switched to carrot juice when breastfeeding, and gave water to the third group when pregnant and breastfeeding. When the babies were five months old, the researchers gave the infants plain and carrot-flavored cereal, only to find that babies who had been exposed to carrot juice while in the womb were more willing to eat carrot cereal.
An alternate theory lays in the kinds of food we eat, specifically, “health food” or indulgent foods. New research from Yale University has found that when people eat healthy food, regardless of how many calories consumed, their stomach signals less satisfaction.
Researchers in the study focused on the hunger hormone called ghrelin, which stimulates one’s appetite. Not surprisingly, ghrelin levels typically increase before meals and decrease after meals. The higher the levels of the hormone, the more likely a person will overeat.
Participants in the study were given identical shakes in order to test whether physiological satiation as measured by ghrelin may vary depending on the mindset in which one approaches consumption of food.
On 2 separate occasions, participants consumed a 380-calorie milkshake under the pretense that it was either a 620-calorie “indulgent” shake or a 140-calorie “sensible” shake. Ghrelin was measured via intravenous blood samples at 3 time points: baseline, anticipatory, and post-consumption. During the first interval participants were asked to view and rate the (misleading) label of the shake. During the second interval participants were asked to drink and rate the milkshake.
The amount of hunger hormones released before consuming the “indulgent” shake was higher than the amount released before drinking the “sensible” shake. Participants who consumed the shakes perceived as being more indulgent reported greater satiation afterward. In other words, if you think of the food as being decadent or indulgent, you might feel more satisfied.
Participants’ satiety was consistent with what they believed they were consuming rather than the actual nutritional value of what they consumed. Therefore, state of mind may have influence over what makes a person feel satisfied after a meal.
If you want to keep your cravings at bay, then consider what research has found. When you understand the culprits behind cravings, you can help control them. Remember, don’t be a slave to the foods you crave!
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Tags: control, crave, food, research, satiety
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Monday, June 6th, 2011
The 2010 Dietary Guidelines for Americans committee report recommends that individuals reduce their sodium consumption. As they search for alternative ways to emphasize flavor in lieu of using salt, much attention has been given to monosodium glutamate (MSG), the flavor enhancer most often associated with Chinese food and after-dinner headaches.
In 1907, Kikunae Ikeda, a professor of physical chemistry at the University of Tokyo, pondered the unique taste of kelp (konbu) and meat. Ikeda initiated an investigation to identify the taste component of dried konbu and discovered that the sodium salt of glutamic acid (ie, MSG) was responsible. He termed this flavor umami. Umami is described as the meaty or savory flavor found in many types of seafood, seaweed, fish, meats, and mushrooms.[1]
Scientists have recently identified several distinct umami receptors.[2] The receptors found on the anterior and posterior taste buds may explain umami’s complex and varied taste. Many questions about this curious flavor remain unanswered; therefore, umami is under evaluation for its relationship with satiety, taste preferences, and even obesity.
A new study found that people who eat more MSG are more likely to be overweight or obese even after accounting for the total number of calories they ate.
Ka He, a nutrition expert at the University of North Carolina, Chapel Hill, who led the study, said that although the risk of weight gain attributable to MSG was modest, the implications for public health are substantial.
MSG is one of the world’s most widely used food additives. Although it tends to be more popular in Asian countries (average intakes range between a gram-and-a-half and 10 grams a day), Americans manage to get their share in processed foods (average intakes are estimated to be half a gram per day), from chips to canned soups, even when it’s not labeled as such. Glutamate has been identified in green tea, seaweed, tomatoes, potatoes, Chinese cabbage, soybeans, Parmesan cheese, sardines, prawns, and clams.[3] Although the FDA considers MSG sage, some people complain of headaches, nausea and other bad reactions it.
Several studies have examined the potential link between MSG and body weight, with conflicting results. In the latest research, published in the American Journal of Clinical Nutrition, He and his colleagues followed more than 10,000 adults in China for about 5.5 years on average.
The researchers measured MSG intake and asked people to estimate their intake over three 24-hour periods. Men and women who ate the most MSG (a median of 5 grams a day) were about 30 percent more likely to become overweight by the end of the study than those who ate the least amount (less than a half-gram a day). After excluding people who were overweight at the start of the study, the risk rose to 33 percent.
Obesity is not as much of a problem in China as it is in the United States, which might suggest that MSG is not a significant culprit in weight gain. However, He explains, the Chinese tend to be physically active, which might help offset the pound-producing properties of the additive.
Why MSG and weight gain may be linked isn’t clear, He added, but it may have something to do with the hormone leptin, which regulates appetite and metabolism. He’s group found that people who consumed more MSG produced more leptin, which could explain why people who ate more MSG gained weight regardless of how many calories they consumed.
But Ivan E. de Araujo, a Yale University neurobiologist who has studied the effects of MSG on leptin, was not convinced by the new findings.
Leptin is released by fat cells, so as people gain weight they have more leptin in their blood, Araujo said. The effect of MSG on leptin levels, then, may simply be a reflection of growing body mass. Araujo also noted that people who consumed the most MSG also consumed the most salt in their diets, which can itself cause water retention and weight gain.
The link between MSG consumption and increased body weight may have many explanations, some of which may include the most recent findings that MSG/glutamate may have one or more metabolic effects in the body which might predispose consumers to weight gain.
What is required now is for more work to be done to assess what effects MSG might have on human physiology that might cause weight gain. If one of the most commonly used food additives recognized as safe does indeed have the potential to cause weight gain, then it’s only right that we should know.
[1] Chaudhari N, Pereira E, Roper SD. Taste receptors for umami: The case for multiple receptors. Am J Clin Nutr. 2009;90(suppl):738S-742S.
[2] Chaudhari N, Pereira E, Roper SD. Taste receptors for umami: The case for multiple receptors. Am J Clin Nutr. 2009;90(suppl):738S-742S.
[3] Kurihara K. Glutamate: From discovery as a food flavor to role as a basic taste (umami). Am J Clin Nutr. 2009;90(suppl):719S-722S.
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Tags: monosodium glutamate, MSG, obesity, research
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Monday, May 23rd, 2011
When schools cut physical education programs so students can spend more time in the classroom, not only are they missing a chance to prevent obesity, they may also be missing an a golden opportunity to promote learning, according to a recent study presented at the Pediatric Academic Societies (PAS) annual meeting in Denver on May 1, 2011.
Researchers sought to determine how implementing a daily physical activity program that incorporated classroom lessons would affect student achievement. First- through sixth-graders at an academically low-scoring elementary school in Charleston, S.C., took part in the program 40 minutes a day, five days a week. Prior to initiation of the program, students spent only 40 minutes per week in physical education classes.
The program involved using several classrooms, which were revamped into two gyms that housed equipment for an All Minds Exercise (AMX) room for older students and an Action Based Learning (ABL) lab for the younger children.
Younger students moved through stations in the ABL lab, learning developmentally appropriate movement skills while basic academic skills were reinforced. For example, children hopped through ladders while naming colors on each rung. Older students had access to exercise equipment with TV monitors. For instance, a treadmill had a monitor that played geography lessons as the student ran through the scene.
Researchers compared state standardized reading test scores for the year before and the year after initiation of the program. Results showed that the time spent out of a traditional classroom in order to increase physical education improved student test scores. The percentage of students reaching their goal on the state tests increased from 55 percent before the program was initiated to 68.5 percent after the program was initiated.
This study adds to growing evidence that exercise is good not only for the body but also the mind. It also shows that physical education and academic instruction need not be mutually exclusive.
There has been much discussion about cutting out recess and P.E. classes so children can have more time in the classroom for instruction. It’s hard to imagine kids sitting still for eight hours a day and maintaining a high level of concentration. Aside from the issue of concentration, another recent study in the Medicine & Science in Sports & Exercise also found that individuals who sit for most of the day are 54 percent more likely to die of heart attacks.
Much blame has been placed on fast food, school lunch, soda intake and video games. Perhaps the answer also lies in this common sense approach to learning that includes movement. Providing activity in a safe school environment makes sense for both weight control and better school performance.
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Tags: activity, children, classroom, education, obesity, physical, research, schools, students
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