Whole Grains and Belly Fat
For the last few weeks I've been writing about the effects of the Mediterranean
Diet in general and some of the specific components of the Mediterranean
Diet on abdominal fat deposition (read: belly fat). My patients are
often concerned about belly fat, not because of its effects on their
health, but because they don't like the way it looks. The truth is
that abdominal fat is a good indicator of greater risks to your health.
Mediterranean Diet Helps Prevent Central Fat Distribution
In last week's Dr. Tim Says.... column I wrote about the
effects of a Mediterranean-style diet on central adiposity - otherwise
known as
"belly fat." I recently ran across a study conducted in Spain
that compares three different diets head-to-head on their effects
on the distribution of belly fat, so I thought I'd share it with
you (Diabetes Care 2007(30): 1717-1723).
What is the best diet for Metabolic Syndrome?
There is excellent research to prove that the optimum diet for metabolic syndrome is a Mediterranean style diet. This article from theJournal of the American College of Cardiology reinforces the conclusions from the last 20 years of research: The Effect of Mediterranean Diet on Metabolic Syndrome and its Components.
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Metabolic syndrome, for those who might not be long-time readers of Dr. Gourmet's Health and Nutrition Bites, is a combination of abnormal lab results and body measurements that, taken together, lead to a greater risk of developing type 2 diabetes, heart disease, stroke, and heart attack. The clinical definition of metabolic syndrome is applied to those meeting three of the following criteria:
For many people, losing weight can help with many of these factors, as can improving your diet. Research into the effects of whole grains has focused on several of these criterion, including improving your Waist to Hip ratio (waist measurement) (Bite, 12/15/10), improving your blood sugars (improving your score in a 2-hour insulin reaction test) and improving cholesterol scores(Bite, 12/19/07). Researchers in Italy and Sweden noted that these (and other) studies lack two elements that would make them even more useful to physicians like myself: they do not directly compare a diet high in whole grains with a diet high in refined grains, nor do they limit their participants to those who already have metabolic syndrome. As you might guess, helping my patients avoid developing metabolic syndrome in the first place is more straightforward than treating those who have already developed the syndrome: specific research on those with the syndrome is especially helpful.
The study, published in Nutrition, Metabolism & Cardiovascular Diseases (2014;24(8):837-844), included 54 men and women between the ages of 40 and 65 who had been diagnosed with metabolic syndrome. For a four-week run-in period they followed their usual diet, then for another 12 weeks they were randomly assigned to one of two diets: a whole grain diet or a refined-grain diet. These were defined as the participant's usual diet with the addition of a fixed amount of whole-grain or refined-grain products, provided free of charge by the researchers, to be consumed as the participant's main source of carbohydrates. The participants were instructed to maintain their starting weight throughout the study.
At the start of the study and every four weeks thereafter the participants spent a day in the lab so that their blood glucose, waist measurements, and cholesterol scores could be tested, as well as measuring their blood insulin concentrations both fasting and after eating a standardized meal for their diet (whole grain or refined grain, as appropriate). To make sure that both groups were adhering to their assigned diet, the researchers also tested the participants' blood for alkylresorcinol concentration, which is a biomarker of whole wheat and rye intake.
Unsurprisingly, neither group lost weight or decreased their waist measurement over the course of the study. Nor were there significant effects on fasting glucose levels, insulin, or cholesterol.
More significantly, however, the whole-grain group's postprandial (after eating) insulin response decreased significantly: the whole-grain group's insulin concentration was 29% lower than the refined-grain group. Higher insulin levels after eating is a known risk factor for type 2 diabetes and heart disease. Similarly, postprandial triglyceride levels were also significantly lower (as much as 43%) in the whole-grain group, with higher levels another possible risk factor for heart disease.
This is a particularly well-designed study that could only be improved by a longer duration and a larger group of participants. It clearly shows that more whole grains in the diet can help you avoid developing type 2 diabetes and heart disease - even if you already have been diagnosed with metabolic syndrome. Here are some simple suggestions for getting more whole grains in your diet.
First posted: July 30, 2014