Mostrando postagens com marcador Diet strategies. Mostrar todas as postagens
Mostrando postagens com marcador Diet strategies. Mostrar todas as postagens
quarta-feira, 26 de agosto de 2015
domingo, 16 de agosto de 2015
Low-fat diet results in more fat loss than low-carb diet in humans
 This is an artistic depiction of a study investigating whether low-fat or low-carb diets lead to more fat burning and fat loss. Credit: Kevin Hall A study from the US National Institutes of Health presents some of the most precise human data yet on whether cutting carbs or fat has the most benefits for losing body fat. In a paper published August 13 in Cell Metabolism, the researchers show how, contrary to popular claims, restricting dietary fat can lead to greater body fat loss than carb restriction, even though a low-carb diet reduces insulin and increases fat burning. Since 2003, Kevin Hall, PhD--a physicist turned metabolism researcher at the National Institute of Diabetes and Digestive and Kidney Diseases--has been using data from dozens of controlled feeding studies conducted over decades of nutrition research to build mathematical models of how different nutrients affect human metabolism and body weight. He noticed that despite claims about carbohydrate versus fat restriction for weight loss, nobody had ever measured what would happen if carbs were selectively cut from the diet while fat remained at a baseline or vice versa. His model simulations showed that only the carb-restricted diet would lead to changes in the amount of fat burned by the body, whereas the reduced-fat diet would lead to greater overall body fat loss, but he needed the human data to back it up. "A lot of people have very strong opinions about what matters for weight loss, and the physiological data upon which those beliefs are based are sometimes lacking," Hall says. "I wanted to rigorously test the theory that carbohydrate restriction is particularly effective for losing body fat since this idea has been influencing many people's decisions about their diets." Studying the effects of diet on weight loss is often confounded by the difficulty in measuring what people actually eat--participants may not adhere to meal plans, misjudge amounts, or are not truthful in follow-up surveys. To counter this, Hall and colleagues confined 19 consenting adults with obesity to a metabolic ward for a pair of 2-week periods, over the course of which every morsel of food eaten was closely monitored and controlled. To keep the variables simple, the two observation periods were like two sides of a balance scale: during the first period, 30% of baseline calories were cut through carb restriction alone, while fat intake remained the same. During the second period the conditions were reversed. Each day, the researchers measured how much fat each participant ate and burned and used this information to calculate the rate of body fat loss. At the end of the two dieting periods, the mathematical model proved to be correct. Body fat lost with dietary fat restriction was greater compared with carbohydrate restriction, even though more fat was burned with the low-carb diet. However, over prolonged periods the model predicted that the body acts to minimize body fat differences between diets that are equal in calories but varying widely in their ratio of carbohydrate to fat. "There is one set of beliefs that says all calories are exactly equal when it comes to body fat loss and there's another that says carbohydrate calories are particularly fattening, so cutting those should lead to more fat loss," Hall says. "Our results showed that, actually, not all calories are created equal when it comes to body fat loss, but over the long term, it's pretty close." Hall does caution against making sweeping conclusions about how to diet from this study. The study's purpose was to explore the physiology of how equal calorie reductions of fat versus carbs affect the human body. The research is limited by its sample size; only 19 people could be enrolled due to the expense of such research and the restrictiveness of the carefully controlled protocol. However, this study clearly reaches statistical significance. In addition,, the menu that the participants followed does not emulate normal dieting and does not account for what diet would be easier to eat over extended periods. "We are trying to do very careful studies in humans to better understand the underlying physiology that will one day be able to help generate better recommendations about day-to-day dieting," Hall says. "But there is currently a gap between our understanding of the physiology and our ability to make effective diet recommendations for lasting weight loss." Hall recommends that for now, the best diet is the one that you can stick to. His lab will next investigate how reduced-carbohydrate and reduced-fat diets affect the brain's reward circuitry, as well as its response to food stimuli. He hopes these results might inform why people respond differently to different diets. Story Source: The above post is reprinted from materials provided by Cell Press. Note: Materials may be edited for content and length. Journal Reference:
http://www.sciencedaily.com/releases/2015/08/150813130016.htm
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domingo, 15 de fevereiro de 2015
Would you take dieting advice from a friend?
Is a new diet or exercise program working for a friend? If so, there's a good chance that you will try it, too.A person who finds success in a wellness program is more influential in getting friends to sign up than a charismatic, but less successful pal, according to a study by University at Buffalo occupational health researcher Lora Cavuoto. The study, "Modeling the Spread of an Obesity Intervention through a Social Network," was published in the Journal of Healthcare Engineering. "People want to see that positive influence," says Cavuoto, assistant professor in the Department of Industrial and Systems Engineering, School of Engineering and Applied Sciences. "Understanding how social influence affects people's participation in health programs can lead to better-designed wellness interventions." Engineering doctoral candidate Mohammadreza Samadi and engineering graduate student Mahboobeh Sangachin worked with Cavuto on the study. Countless diets and weight-loss programs exist to combat the high rate of obesity among US people. But they do little good if people don't adopt them. Cavuoto's research will help diet and exercise programs reach more people by advising marketers on which people to target as endorsers. The study simulated the behavior of fictional people created using combinations of physical attributes and personality traits, such as the ability to lose weight and a high or low body mass index. The model distributed traits based on national population averages. Based on the simulations, people in social networks linked to someone who successfully lost weight or had a high body mass index produced the largest total weight loss among peers. The networks surrounding a person with a high number of friends -- those who were more charismatic or popular -- produced lower weight-loss totals. Cavuoto's results support the new approach many weight-loss programs have taken in attracting new participants: Celebrity endorsers with a large reach have taken a backseat to everyday people who benefit from a new diet or workout. "Your ties and social contacts may have a bigger effect because you see them every day and you have that close connection," says Cavuoto. "If they can be successful, then that's your best way of getting information out that a program is good." Story Source: The above story is based on materials provided by University at Buffalo. Note: Materials may be edited for content and length. Journal Reference:
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sexta-feira, 14 de novembro de 2014
Live longer? Save the planet? Better diet could nail both
This image shows Dr. G David Tilman at Cedar Creek Ecosystem Science Reserve. Tilman is director of the University of Minnesota research field station.
As cities and incomes increase around the world, so does consumption of refined sugars, refined fats, oils and resource- and land-intense agricultural products such as beef. A new study led by University of Minnesota ecologist David Tilman shows how a shift away from this trajectory and toward healthier traditional Mediterranean, pescatarian or vegetarian diets could not only boost human lifespan and quality of life, but also slash greenhouse gas emissions and save habitat for endangered species.
The study, published in the November 12 online edition of Nature by Tilman and graduate student Michael Clark, synthesized data on environmental costs of food production, diet trends, relationships between diet and health, and population growth. Their integrated analysis painted a striking picture of the human and environmental health costs of our current diet trajectory as well as how strategically modifying food choices could reduce not only incidence of type II diabetes, coronary heart disease and other chronic diseases, but global agricultural greenhouse gas emissions and habitat degradation as well.
"We showed that the same dietary changes that can add about a decade to our lives can also prevent massive environmental damage," said Tilman, a professor in the University's College of Biological Sciences and resident fellow at the Institute on the Environment. "In particular, if the world were to adopt variations on three common diets, health would be greatly increased at the same time global greenhouse gas emissions were reduced by an amount equal to the current greenhouse gas emissions of al all cars, trucks, plans trains and ships. In addition, this dietary shift would prevent the destruction of an area of tropical forests and savannas as large as half of the United States."
The researchers found that, as incomes increased between 1961 and 2009, people consumed more meat protein, empty calories and total calories per person. When these trends were combined with forecasts of population growth and income growth for the coming decades, the study predicted that diets in 2050 would contain fewer servings of fruits and vegetables, but about 60 percent more empty calories and 25 to 50 percent more pork, poultry, beef, dairy and eggs -- a suite of changes that would increase of type II diabetes, coronary heart disease and some cancers. Using life-cycle analyses of various food production systems, the study also calculated that, if current trends prevail, these 2050 diets would also lead to an 80 percent increase in global greenhouse gas emissions from food production as well as habitat destruction due to land clearing for agriculture around the world.
The study then compared health impacts of the global omnivorous diet with those reported for traditional Mediterranean, pescatarian and vegetarian diets. Adopting these alternative diets could reduce incidence of type II diabetes by about 25 percent, cancer by about 10 percent and death from heart disease by about 20 percent relative to the omnivore diet. Additionally, the adoption of these or similar alternative diets would prevent most or all of the increased greenhouse gas emissions and habitat destruction that would otherwise be caused by both dietary changes and increased global population.
The authors acknowledged that numerous factors go into diet choice -- but also pointed out that the alternative diets already are part of the lives of countless people around the world. Noting that variations on the diets used in the scenario could potentially show even greater benefit, they concluded that "the evaluation and implementation of dietary solutions to the tightly linked diet-environment-health trilemma is a global challenge, and opportunity, of great environmental and public health importance."
Story Source:
The above story is based on materials provided by University of Minnesota. Note: Materials may be edited for content and length.
Journal Reference:
- David Tilman, Michael Clark. Global diets link environmental sustainability and human health. Nature, 2014; DOI: 10.1038/nature13959
domingo, 9 de novembro de 2014
Time spent preparing meals at home linked to healthier diet
Time may be one of the most essential ingredients for a healthy diet, finds new research in the American Journal of Preventive Medicine.
Spending more time at home preparing meals is associated with several indicators of a better diet, such as eating more fruits and vegetables. Conversely, spending less than an hour a day preparing food at home is associated with eating more fast food and spending more money eating out.
"There is very little data on the time cost of healthy eating," said Pablo Monsivais, Ph.D., M.P.H., the study's lead author and a senior university lecturer with the Center for Diet and Activity Research at the University of Cambridge School of Clinical Medicine in England.
The findings are based on responses from 1,319 adults who participated by phone in the Seattle Obesity Study in 2008 and 2009. Participants answered questions about how many hours a day they averaged preparing and cooking food and cleaning up after meals. They also reported on food consumption and spending, as well as use of restaurants. About 16 percent of participants said they spent less than one hour a day on meal preparation. About 43 percent reported spending between one and two hours per day on meal preparation, while 41 percent said they spent more than two hours a day on it.
Employment outside the home was associated with fewer hours spent preparing meals. Notably, about two-thirds of those who reported that they prepped, cooked and cleaned up were women. People with less time available for meal preparation also appear to value convenience, choosing more often to eat out or to buy fast food and ready-made foods to eat at home.
"This study reinforces what previous studies and nutrition practice tells us: that time is commonly reported as a barrier to healthy eating," said Lauri Wright, Ph.D., R.D.N., a registered dietician and nutritionist and assistant professor in the Department of Community and Family Health at the University of South Florida in Tampa.
Wright, a spokesperson for the Academy of Nutrition and Dietetics, reiterated an observation made in the study: "Besides time and cost, people often don't feel confident about their ability to prepare healthy meals."
Wright added, "Registered dietician/nutritionists give close consideration to the issue of time when making their recommendations. They can give tips on ways to optimize time and money, such as planning meals, shopping ahead and preparing some foods in advance that can allow families to have quick-to-prepare healthy meals and snacks."
Story Source:
The above story is based on materials provided by Health Behavior News Service, part of the Center for Advancing Health. The original article was written by Valerie DeBenedette. Note: Materials may be edited for content and length.
Journal Reference:
- Pablo Monsivais, Anju Aggarwal, Adam Drewnowski. Time Spent on Home Food Preparation and Indicators of Healthy Eating. American Journal of Preventive Medicine, 2014; DOI: 10.1016/j.amepre.2014.07.033
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