Written by Greg Arnold, DC, CSCS. In a study of 264 healthy women, those with the highest intake of soluble fiber had a 48% reduced risk of having insulin resistance.
According to the Center for Disease Control and Prevention, over 66% of Americans are overweight (having a Body Mass index (BMI) between 25 and 29.9 kg/m2) and 32% of Americans are obese (having a Body Mass Index > 30 kg/m2) (1, 2). In 2008, medical costs associated with obesity was nearly $147 billion, with the annual cost of treating obese patients $1,429 higher than those of normal weight (3). Obesity increases the risk for several chronic diseases, including heart disease ($108.9 billion in healthcare costs) (4), stroke ($38.6 billion in healthcare costs (5)), and type 2 diabetes ($174 billion in healthcare costs (6)).
Now a new study (7) suggests fiber intake, physical activity, and body fat % all play a role in helping maintain insulin sensitivity, a key function in controlling blood sugar and helping prevent the onset of chronic disease.
In the study, 264 healthy, non-smoking, premenopausal women between the ages of 37 and 43 underwent a physical examination that include height, weight, body fat %, and provided blood samples to measure for insulin resistance. They were then given a digital food scale and 7-day food diary to record all food intake as well as an accelerometer to measure physical activity levels. The researchers used a formula called the Homeostasis Model Assessment of Insulin Resistance (HOMA-IR), a very reliable method of measuring insulin resistance (8). The researchers called the subjects twice over the 7-day period to confirm the dietary food records were being kept and to answer any questions.
The researchers found a significant benefit of fiber intake on HOMA-IR levels, specifically for soluble fiber, with every 1-gram increase in soluble fiber produced an average decrease of 7.4% (0.112) in in HOMA-IR (p = 0.0051). They also found that those with the highest 25% of soluble fiber intake (6.5 grams per 1,000 calories) had a 48% reduced risk of having insulin resistance compared to those with the lowest soluble fiber intake (0.2 grams per 1,000 calories) (p ) and the soluble fiber intake came most often from starchy vegetable intake. No significant effects on HOMA-IR was seen with insoluble fiber intake.
The benefits of soluble fiber intake, however, were significantly influenced by both body fat % and physical activity. Specifically, the greater the physical activity of the subjects, the lower their body fat % and this led to a greater effect of soluble fiber in decreasing HOMA-IR. When physical activity levels were low, body fat % was higher and the significance of soluble fiber on HOMA-IR significantly decreased.
Unfortunately, the researchers did not provide data on specific physical activity levels and body fat % on soluble fiber intake in decreasing HOMA-IR, instead stating “if all women had the same body fat percentage, the relationship between soluble fiber and insulin resistance would be weaker and the total fibre/HOMA-IR relationship would not exist.”
When suggesting how soluble fiber intake benefits insulin sensitivity, the researchers pointed to the ability of soluble fiber to slow digestion in the stomach and produce a slower release of sugar into the blood stream which leads to greater control of insulin levels (9). They went on to conclude, “independent from [physical activity levels and body fat %], soluble fiber remains a good predictor of lower levels of insulin resistance.”
Source: Breneman, Charity B., and Larry Tucker. “Dietary fibre consumption and insulin resistance–the role of body fat and physical activity.” British Journal of Nutrition 110.02 (2013): 375-383.
© The Authors 2012
Posted August 16, 2013.
Greg Arnold is a Chiropractic Physician practicing in Hauppauge, NY. You can contact Dr. Arnold directly by emailing him at PitchingDoc@msn.com or visiting his web site at www.PitchingDoc.com
References:
- Childhood Obesity” posted on the CDC Website.
- “Defining Overweight and Obesity” posted on the CDC website.
- “Adult Obesity Facts” posted on the CDC website.
- “Heart Disease Facts” posted on the CDC website.
- “Stroke Facts” posted on the CDC website.
- “2011 Diabetes Fact Sheet” posted on the CDC website.
- Breneman CB. Dietary fibre consumption and insulin resistance – the role of body fat and physical activity. Br J Nutr.2013 Jul;110(2):375-83. doi: 10.1017/S0007114512004953.
- Matthews DR. Homeostasis model assessment: insulin resistance and beta-cell function from fasting plasma-glucose and insulin concentrations in man. Diabetologia 1985; 28, 412–419.
- Jenkins DJA. Dietary fibre, lente carbohydrates and the insulin-resistant diseases. Br J Nutr 2000; 83, S157–S163.
