Wednesday, June 22, 2011

Omega-3 boosts insulin resistance markers, suggests study

By Nathan Gray, 16-Jun-2011

Increased consumption of omega-3 fatty acids may help to improve important markers insulin resistance, which may lead to diabetes, says new research.

The study, published in the European Journal of Lipid Science and Technology, evaluated the effects of omega-3 polyunsaturated fatty acids (PUFAs) on lipid profile and insulin resistance biomarkers. The researchers found that dietary intake of concentrated omega-3 capsules with meals resulted in improved lipid profiles and adiponectin levels, compared to placebo in a baseline condition, and an improvement of all insulin resistance parameters after an oral fat load.

“Omega-3 PUFA not only improved lipid profile in a baseline situation, but it also improved all insulin resistance parameters in a post-prandial situation simulated with an oral fat load. This is another important action,” said the researchers, led by Giuseppe Derosa from the University of Pavia, Italy.

Omega-3

The beneficial effects of dietary intake of omega-3 PUFA and cardiovascular disease first established following the observation that the Greenland Inuits had low mortality from coronary heart disease despite a fat-rich diet.

Since then, research has demonstrated omega-3 fatty acids can improve the plasma lipid profiles, boost inflammatory responses, and reduce blood pressure, pulse pressure, and basal heart rate.

Study details

For the study, 167 patients (82 males and 85 females) were assigned to receive one gram of either placebo (a capsule containing sucrose, mannitol, and mineral salts) or omega-3 PUFA (concentrated EPA and DHA) three times a day, during meals, for six months.
 
Omega-3 PUFAs were reported to improve HDL-cholesterol and plasma triglyceride markers compared to placebo, while they had a neutral effect on total cholesterol and LDL-cholesterol.
After an oral fat load, the researchers found that the group taking omega-3 capsules showed an improvement of all parameters, include insulin resistance biomarkers, while there was a neutral effect with placebo.

Derosa and his colleagues concluded that omega-3 intake “resulted in a greater improvement of lipid profile and ADN compared to placebo in a baseline condition, and an improvement of all insulin resistance parameters after an oral fat load.”

Source: European Journal of Lipid Science and Technology
Published online ahead of print, doi: 10.1002/ejlt.201000504

“Effects of n-3 PUFA on insulin resistance after an oral fat load”
Authors: G. Derosa, A.F.G. Cicero, E. Fogari, A. D'Angelo, A. Bonaventura, P. Maffioli

Calcium and weight loss: Effects are small but significant, says review

By Stephen Daniells, 07-Jun-2011
Related topics: Research, Minerals, Weight management

Calcium containing dietary supplements may produce ‘small, statistically significant weight loss’, according to a new meta-analysis.


Calcium may aid weight loss, says meta-analysis
Calcium may aid weight loss, says meta-analysis

Data from seven eligible trials showed that calcium may provide weight loss of around 1.5 kg per year, compared with placebo, according to results published in Nutrition Reviews.
In addition, a daily dose of 1,000 milligrams of calcium was associated with a “small, significant reduction in body fat” of about 2 kg per year, report the scientists, led by Igho Onakpoya from the Department of Complementary Medicine, Peninsula Medical School at the University of Exeter, UK.
“The present analysis indicates that evidence on calcium supplementation and weight management from published RCTs is scarce, and most RCTs have not been rigorously reported,” wrote the researcher.

“While the findings suggest that calcium supplementation for at least 6 months results in a statistically significant weight loss in obese and overweight individuals, the clinical relevance of this finding is uncertain,” they added.

Conflict or confusion?

The potential role of dairy, and the calcium it contains, for weight management is an area of ongoing debate. A relationship between dairy intake and weight reduction has been recorded in numerous studies, and dairy industries in Europe and the US have been promoting milk-based products for consumers who want to slim for some time.

There are even splits within the dairy camp, with some arguing that calcium and vitamin D are the active nutrients behind the effects. One of the lead researchers in this area, Dr Michael Zemel from the University of Tennessee, has previously said that dairy can help reduce body fat and that calcium only accounts for about 40 per cent of the effect.

Clarity

In an accompanying editorial in the same journal, Robert Heaney from Creighton University in Nebraska said the meta-analysis afforded “an opportunity to clarify some of the confusion surrounding this issue”.
For a 140 kg woman seeking to lose half of her body weight, the mean weight loss calculated by Prof Ernst and his co-workers of about 1.5 kg per year would “have very limited interest.
“However, for a population confronting secular weight gain (e.g., otherwise healthy women atmid-life), this same weight effect is huge,” he said.

Prof Heaney added that there are four main conclusions that could responsibly be drawn from the meta-analysis: In addition to countering the weight gain that may occur in mid-life, calcium “should be a component of any weight loss regimen, as it augments the weight loss of a caloric deficit while protecting lean body mass; [it] is not a substitute for control of an energy intake/output imbalance; and [calcium] is not a drug and is certainly not a magic bullet”.

How?

Onakpoya and his co-workers noted that reports in the literature do support biological plausibility for calcium to aid body weight and fat loss: One such mechanism could involve a decrease in levels of 1,25-vitamin D – the active form of the vitamin – which in stimulates the breakdown of fat and inhibits the action of fat cells.

There are also reports that indicate that a diet rich in calcium may promote the oxidation of fat, “resulting in the removal of additional amounts of calories from the body”.
Source: Nutrition Reviews

Volume 69, Issue 6, Pages: 335-343, doi:10.1111/j.1753-4887.2011.00397.x
“Efficacy of calcium supplementation for management of overweight and obesity: systematic review of randomized clinical trials”

Authors: I.J. Onakpoya, R. Perry, J. Zhang, E. Ernst

Tuesday, June 21, 2011

Fat Substitutes Linked To Weight Gain

Synthetic fat substitutes used in low-calorie potato chips and other foods could backfire and contribute to weight gain and obesity, according to a study published by the American Psychological Association.

The study, by researchers at Purdue University, challenges the conventional wisdom that foods made with fat substitutes help with weight loss. "Our research showed that fat substitutes can interfere with the body's ability to regulate food intake, which can lead to inefficient use of calories and weight gain," said Susan E. Swithers, PhD, the lead researcher and a Purdue psychology professor. The study was published online in the APA journal Behavioral Neuroscience.

The study used laboratory rats that were fed either a high-fat or low-fat diet of chow. Half of the rats in each group also were fed Pringles potato chips that are high in fat and calories. The remaining rats in each group were fed high-calorie Pringles chips on some days and low-calorie Pringles Light chips on other days. The Pringles Light chips are made with olestra, a synthetic fat substitute that has zero calories and passes through the body undigested.

For rats on the high-fat diet, the group that ate both types of potato chips consumed more food, gained more weight and developed more fatty tissue than the rats that ate only the high-calorie chips. The fat rats also didn't lose the extra weight even after the potato chips were removed from their diet. "Based on this data, a diet that is low in fat and calories might be a better strategy for weight loss than using fat substitutes," Swithers said. However, she warned that it can be difficult to extrapolate laboratory findings about rats to people, even though their biological responses to food are similar. The study was conducted by Swithers along with Purdue psychology professor Terry L. Davidson, PhD, and former Purdue undergraduate student Sean Ogden.

Why would a fat substitute confuse the body? Food with a sweet or fatty taste usually indicates a large number of calories, and the taste triggers various responses by the body, including salivation, hormonal secretions and metabolic reactions. Fat substitutes can interfere with that relationship when the body expects to receive a large burst of calories but is fooled by a fat substitute.

There is some good news if a diet is naturally low in fat. The rats that were fed a low-fat diet didn't experience significant weight gain from either type of potato chips. However, when those same rats were switched to a high-fat diet, the rats that had eaten both types of potato chips ate more food and gained more weight and body fat than the rats that had eaten only the high-calorie chips.

Swithers and Davidson have reported similar findings in previous rat studies that showed saccharin and other artificial sweeteners also can promote weight gain and increased body fat. The use of artificial sweeteners and fat substitutes has increased dramatically over the past 30 years, mirroring the increase in obesity in America. Dieters have turned to these artificial means to lower calories while still eating foods that taste sweet or fatty. So what is a dieter supposed to do to drop a size?

"Unfortunately, there is no silver bullet," Swithers said. "Eating food which is naturally low in fat and calories may be a better route than relying on fat substitutes or artificial sweeteners."

Source: American Psychological Association (APA)

Calorie-Burning Brown Fat Is a Potential Obesity Treatment, Researchers Say

A new study suggests that many adults have large amounts of brown fat, the "good" fat that burns calories to keep us warm, and that it may be possible to make even more of this tissue.


The study's lead author, Aaron Cypess, MD, PhD, is presenting the results at The Endocrine Society's 93rd Annual Meeting in Boston.

"We are now even more optimistic that brown fat could be used for treating obesity and diabetes," said Cypess, an assistant professor at Harvard Medical School and the Joslin Diabetes Center in Boston.
Cypess heads the research team that two years ago published a study showing that brown fat is present in adults, not just in infants and small mammals, as scientists had thought. Although most adult fat is calorie-storing white fat, most adults have some brown fat in an area extending from the front of the neck to the chest, he reported at The Endocrine Society's meeting in 2009.

Now they have learned that brown fat cells lie in deeper fat, not superficial fat, and that the number of regions of brown fat varies by person, Cypess reported. They discovered this by measuring the expression of a protein found exclusively in brown fat, called uncoupling protein-1. However, even in those regions where many brown fat cells are present, they are mixed with white fat cells.

"It's a marbling at the cellular level," Cypess said. "We wondered: Wouldn't it be nice if you could grow more brown fat? The answer is yes."

In their new study, the researchers succeeded in growing mature human brown fat cells from preadipocytes, or pre-fat cells, that they obtained from a fresh sample of brown fat taken from the neck of a patient having routine surgery. The process took about two weeks in a laboratory dish but likely occurs more quickly in the body, Cypess said.

"Some of these preadipocytes may have the choice to become either white or brown fat," he said.
In another experiment, Cypess and his colleagues measured how many calories brown fat burns. To do so, they measured the fat cells' oxygen consumption rate in both cultures and surgical tissue samples from volunteers.

"We demonstrated that brown fat burns up a substantial number of calories," Cypess said. "We have an organ in our body whose job it is to generate heat and burn calories."

Although Cypess said stimulating the growth of additional brown fat may be a promising treatment of obesity, it cannot replace traditional approaches such as diet and exercise. He said, "As powerful as brown fat could be at burning calories, we can easily out-eat the benefit."

The National Institutes of Health and the Eli Lilly Foundation funded this study.

Strawberries Boost Red Blood Cells

A group of volunteers ate half a kilo of strawberries every day for two weeks to demonstrate that eating this fruit improves the antioxidant capacity of blood. The study, carried out by Italian and Spanish researchers, showed that strawberries boost red blood cells' response to oxidative stress, an imbalance that is associated with various diseases.
Scientists have previously tried to confirm the antioxidant capacity of strawberries using in vitro laboratory experiments. Now, a team of researchers from the Marche Polytechnic University (UNIVPM, in Italy) and the University of Granada (UGR, in Spain) have demonstrated this effect in vivo, in a study on human volunteers published in the journal Food Chemistry.
Each day, the scientists fed 12 healthy volunteers 500 grams of strawberries (of the 'Sveva' variety) over the course of the day. They took blood samples from them after four, eight, 12 and 16 days, and also a month later. The results show that regular consumption of this fruit can improve the antioxidant capacity of blood plasma and also the resistance of red blood cells to oxidative haemolysis (fragmentation).

"We have shown that some varieties of strawberries make erythrocytes more resistant to oxidative stress. This could be of great significance if you take into account that this phenomenon can lead to serious diseases," Maurizio Battino, lead author of the study and a researcher at the UNIVPM, said.
The team is now analysing the variations caused by eating smaller quantities of strawberries (average consumption tends to be a 150g or 200g bowl per day). "The important thing is that strawberries should form a part of people's healthy and balanced diet, as one of their five daily portions of fruit and vegetables," Battino points out.

"Various strawberry varieties are also being analysed in the laboratory, since they each contain antioxidants in differing amounts and proportions," explains José Luis Quiles, the Spanish participant in the study and a researcher at the UGR.

The body has an extensive arsenal of very diverse antioxidant mechanisms, which act at different levels. These can be cellular tools that repair oxidised genetic material, or molecules that are either manufactured by the body itself or consumed through the diet, which neutralise free radicals. Strawberries contain a large amount of phenolic compounds, such as flavonoids, which have antioxidant properties.

These substances reduce oxidative stress, an imbalance that occurs in certain pathologies, (such as cardiovascular disease, cancer and diabetes) and physiological situations (birth, aging, physical exercise), as well as in the battles between "reactive kinds of oxygen" -- in particular free radicals -- and the body's antioxidant defences.

When the level of oxidation exceeds these antioxidant defences, oxidative stress occurs. Aside from causing certain illnesses, this is also implicated in phenomena such as the speed at which we may age, for example.