A Belly-fighting Tip That's for Real
Not all body fat is created equal. Some people accumulate fat predominantly in the belly, while in others fat deposits are spread all around, and it does matter, because belly fat presents a higher risk for chronic diseases. Think of belly fat as a big, active endocrine gland secreting risky substances - abdominal or visceral fat is especially active metabolically and plays a part in insulin resistance and diabetes, lipid abnormalities, hypertension and cardiovascular disease.
And here's another piece of worrying news: The majority of Americans are now overweight or obese, and the extra padding we've added as a population has accumulated preferentially in the worst location for our health - our belly - and even people with normal weight seem to be getting wider waistlines.
Why are bellies getting disproportionately bigger? Some ethnic groups - such as Asians, Indians and Hispanics - have a higher tendency to accumulate abdominal fat. Other factors suggested to affect belly fat buildup include lack of exercise.
But does our diet affect where we deposit our fat stores? Does the kind of food we eat determine body shape?
Lifestyle and belly fat
Several studies suggest that sugary drinks and fructose increase fat accumulation in the worst possible locations of our anatomy.
A new study in the journal Obesity followed 1,114 people over 5 years, looking to see if lifestyle factors directed fat preferentially to the belly.
The study population included 339 African Americans (African Americans tend to have lower belly fat than whites or Hispanics) and 775 Hispanic Americans, aged 18-81 years. Participants were asked about their dietary and exercise habits, weight and height were measured at baseline and follow-up visits, and belly fat was measured with an abdominal CT scan. A CT scan is a rather invasive way to measure belly fat, but a very accurate one.
Of all the foods and nutrients considered in the study one single nutrient was most significantly associated with belly fat: Fiber. For every 10 grams of soluble fiber eaten per day, belly fat was reduced by about 4 percent after 5 years -- irrespective of total weight or BMI.
Other studies have shown that reduced fiber diets are associated with weight gain, but this study actually showed that soluble fiber makes fat "choose" a depot that's healthier for us - if you overeat, but eat more soluble fiber, the fat will go under the skin, rather than into the belly.
Oh, and here's one more important finding: Vigorous exercise was also associated with less belly fat.
Fiber: soluble, insoluble, and where to find it
Dietary fiber is a part of plant food that we humans cannot digest, but it nevertheless has many health benefits.
Soluble fiber is fermented by bacteria in the gut and has physiologically active byproducts; insoluble fiber is metabolically inactive, and just absorbs water and creates bulk as it moves through the gut, thus speeding food's passage in the gut and preventing constipation.
Both soluble and insoluble fiber may help in making us feel full on less food, because they add to food bulk while adding no calories. Soluble fiber has shown promise in lowering LDL (bad) cholesterol, regulating blood sugar and prevention of heart disease. Insoluble fiber aids regular bowel movement.
Good sources for soluble fiber include fruits such as apples, bananas, plums, and berries, vegetables such as broccoli and carrots, sweet potatoes and onions, legumes such as soy, peas and other beans, and grains such as oats and barley.
Good sources of insoluble fiber include whole grain foods, bran, nuts and seeds, vegetables such as celery and zucchini, and the skins of many fruits and veggies.
Most Americans get only about 15 grams of fiber per day in their diet, which is half the minimum 25-30 grams recommended.
What about fiber supplements and foods with fiber added to them? It's unclear if added fiber provides the benefits of naturally occurring fiber and the benefits of supplements have not been studied as extensively as those of dietary fibers - the food plant as a whole is usually more than the sum of its known parts.
Fiber for a flat belly
All fruits, veggies whole grains and nuts contribute fiber to our diet. I don't participate in the fiber wars, and wouldn't favor one fruit over another for its fiber quantity or quality. If you eat your fruits and veggies you'll get plenty of fiber - but do try to leave the peel on where appropriate.
Eating fruits and veggies reduces the risk of obesity, but this new study suggests that eating them also enables us to direct where were we deposit our fat even if we do gain weight - dietary fiber may funnel that fat to a more favorable storage area.
Dr. Ayala
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