Can a Modified Fat Diet With Low Glycaemic Load Improve Insulin Sensitivity and Inflammatory Mediators in Overweight People With Chronic Heart Failure?
There is an increasing prevalence of chronic heart failure (CHF) in Western societies. In
the last decade, progress has been made in understanding the neurohormonal involvement in
the progression of the disease and consequently, new treatments have been developed although
the mortality rate still remains high. Chronic heart failure is associated with marked
insulin resistance as well as increasing plasma levels of pro-inflammatory markers such as
Tumor Necrosis Factor-alpha (TNF-alpha) and Interleukin-6 (IL-6) with increasing severity of
the disease. This has recently become an area of increased research interest. In CHF,
insulin resistance may be present even when blood glucose levels appear normal.
Independently of its influence on risk of arteriosclerosis, insulin resistance supports
further progression of heart failure. Hyperinsulinaemia has also been found to worsen
symptomatic status in CHF patients.
The introduction of beta-blockers in the treatment of CHF may have a beneficial effect on
insulin resistance. However, so far tested drugs seem to have little influence on production
of pro-inflammatory markers in CHF patients. The use of beta-blockers in the clinical
setting is also associated with weight gain. While weight gain is of benefit to patients
with cachexia, a common problem in CHF, it is problematic in CHF patients who are already
overweight, particularly since obesity is known to be implicated in the development of
insulin resistance. Because of this, it would seem to be beneficial to prevent further
weight gain in those patients with heart failure who are not cachexic. Weight loss in these
patients, however should also be prevented since obese patients with CHF appear to have the
better prognosis. As change in body weight has important implications for disease
progression, choice of dietary treatment is of particular importance in CHF patients.
Ideally in CHF patients, we should be maintaining body weight while still attempting to
reduce other coronary risk factors such as insulin resistance and atherogenic dyslipidemia.
Traditionally, diet for people with insulin resistance and other features of the metabolic
syndrome has been based on a low fat, high carbohydrate dietary prescription. This has been
questioned recently with emerging clear endorsement of diets that are restricted in
saturated fat (< 10% of total energy [%E]) but by allowing higher amounts of monounsaturated
fat (MUFA), also reduce the diet carbohydrate content and thus the glycaemic load.
Metabolic studies in people with diabetes have shown that modified fat (high MUFA) diets are
more effective than a low fat high carbohydrate diet in improving insulin resistance
although no similar studies are yet available for people with heart failure.
Studies in people with diabetes have also indicated that modified fat (high MUFA) diets are
clearly more beneficial than low fat diets in the effects on triacylglycerols and HDL
cholesterol and they also favorably influence blood pressure, coagulation, endothelial
activation, inflammation, and thermogenic capacity. Modified fat (high MUFA) diets therefore
reduce heart disease risk. Moreover, when the energy density is controlled through
inclusion of plenty of fruit and vegetables, modified fat (high MUFA) diets do not promote
obesity. One final benefit is better acceptance and compliance long term.
Allocation: Randomized, Endpoint Classification: Efficacy Study, Intervention Model: Parallel Assignment, Masking: Open Label
Body mass index (BMI)
Fiona J Adams, BSc. Grad Dip Diet
Dietition on Staff, Alfred Hospital
Australia: National Health and Medical Research Council