News Briefs

Mediterranean diet and managing diabetes
Consuming a Mediterranean style diet is more effective for diabetes management than a low-fat diet, reports a new study published in Annals of Internal Medicine. ‘Participants assigned to the Mediterranean-style diet lost more weight and experienced greater improvements in some glycemic control and coronary risk measures than did those assigned to the low-fat diet,’ wrote the researchers led by Katherine Esposito from the Second University of Naples. In addition to improvements in blood glucose management, the Mediterranean-style diet also delayed the need for anti-hyperglycemic (blood glucose lowering) drug therapy. ‘Perhaps most important, the findings reinforce the message that benefits of lifestyle interventions should not be overlooked despite the drug-intensive style of medicine fueled by the current medical literature,’

Esposito and her co-workers recruited 215 overweight people with newly diagnosed type-2 diabetes and randomly assigned them to consume the Mediterranean-style diet or a low-fat diet. After four years, only 44% of people in the Mediterranean-style diet group required anti-hyperglycemic drug treatment, compared to 70% in the low-fat diet group.

What did they eat? The Mediterranean diet was rich in vegetables and whole grains and low in red meat, which was replaced with poultry and fish. The low-fat diet was based on American Heart Association guidelines; it too was rich in whole grains and restricted additional fats, sweets, and high-fat snacks. The researchers note two primary limitations of their study: 1) it was not double-blind, and 2) dietary intakes were self-reported.

GI Group: We know that you are going to be asking exactly the same questions we did: what exactly did the people on the Mediterranean diet eat? We have tried to contact the authors, but at time of publication, had not had a reply. So we asked Johanna Burani who spends a great deal of time in Italy for some comments. ‘I think they are recommending LOTS of vegetables (all kinds) and LOTS of beans (pinto, chickpeas, kidney, garbanzo) and fruit. Under normal conditions, people in Italy wouldn’t willingly choose wholewheat pasta or brown rice but maybe the authors got them to eat these whole grains for the study. I really think the thrust would be towards vegetables and beans -– at least for everyone out here in the trenches.’

Meal timing and weight gain
A new study published in Obesity (in mice) suggests that it’s not just how much you eat, but when you eat it, that influences weight gain. ‘How or why a person gains weight is very complicated, but it clearly is not just calories in and calories out,’ said Prof Fred Turek, director of the Center for Sleep and Circadian Biology at Northwestern University. ‘We think some factors are under circadian control. Better timing of meals … could be a critical element in slowing the ever-increasing incidence of obesity.’

To test whether ‘when you eat’ can affect body weight, the researchers studied two groups of mice and found simply modifying their feeding time alone greatly affected their body weight. Over the six-week study period, the group of mice that ate as much as they liked of a high-fat diet during their normal sleeping hours (our day time) gained significantly more weight than the mice eating the same type and amount of food during their naturally wakeful hours (our night time) although both groups of mice had actually consumed about the same amount of calories and performed the same amount of exercise over the six weeks.

Of course human studies are needed to determine if timing of food intake influences our body weight, but this study suggests that late-night eating may be worse, in terms of weight gain, than eating during normal waking hours says Fred Turek.

GI Group: This study, while only in mice, may also have implications for shift workers.

Age difference and low GI diets
A study published in Diabetologia reports that the benefits of a low GI diet appear to be more pronounced in young adult mice (16 weeks) than in older mice (44 weeks). The dietary intervention involved ‘wild type’ mice and (sorry to be technical here) specially bred mice whose glucose-dependent insulinotropic polypeptide receptor had been knocked out. The study calls them ‘Gipr genotype mice’.

Compared with the young mice on a low GI diet, the young mice on a high GI diet gained a significant amount of weight along with more body fat and reduced insulin sensitivity. With the older mice, the story is more complicated. Though body fat also slightly increased in high GI vs low GI older ‘wild type’ mice, there were no significant changes in their body weight and estimated insulin sensitivity. However, the older Gipr genotype mice on a high GI diet showed significantly lower cumulative net energy intake, increased locomotor activity and improved markers of insulin sensitivity suggesting, say the authors, that inactivation of GIP signalling in aged animals on a high-GI diet could be beneficial.

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