Low-Fat-High-Carb and High-Fat-Low-Carb Diets Exert Same Health Benefits

So many diet fads, so little evidence of efficacy. The single most important thing about what one eats is to ensure that input (commonly defined as calories) doesn't exceed the energy expenditure needs of ones body. Some fad diets espouse the so-called benefits of low-carbohydrate intake, others the so-called benefits low-fat intake. The clinical evidence is quite clear that too little carbohydrate in the diet activates a stronger desire for food, in other words it makes one hungrier, and too little fat in the diet can wreak havoc on ones skin, nails, hair, and most importantly brain functioning. So what does one do then?? As I recently posted on my blog a healthy life extending diet is composed of a balance of macronutrients (protein, carbohydrate, fat) that is in balance with the energy needs of ones body:


Now new clinical research published in the American Journal of Clinical Nutrition demonstrates that when energy intake is controlled so as not to exceed the needs of the body a diet that has more calories from carbohydrate than fat (low-fat, high-carbohydrate: LFHC) or a diet that has more calories from fat than carbohydrate (very high-fat, low-carbohydrate: VHFLC) both result in the same metabolic and heath outcomes:

Visceral adiposity and metabolic syndrome after very high–fat and low-fat isocaloric diets: a randomized controlled trial

This report examined the effects of diet composition in 46 men aged 30-50 years. All of the participants in this study were considered overweight by measures of BMI and waist circumference. Reams of clinical data have proven that intra-abdominal fat accumulation (commonly referred to as central adiposity), as is typical in overweight and obese individuals, is strongly associated with insulin resistance, elevated circulating triglycerides, increased total cholesterol, and reduced levels of high-density lipoproteins, HDL (the so-called "good cholesterol"). All of these pathological changes are associated with what is called the metabolic syndrome. In addition, numerous studies have clearly demonstrated that a sustained reduction in total energy (caloric) intake, that is accomplished either by reduced fat intake or reduced carbohydrate intake, results in significant improvements in health and reductions in the risk for cardiovascular diseases associated with the metabolic syndrome.

Given the known benefits of reduced energy intake in this study, regardless of whether the participants were randomly assigned to the LFHC diet or the VHFLC diet, they were consuming equal amounts of total energy designed to ensure no further weight gain. In addition, both diets contained the same amount of protein and the foods consumed were low-processed, low-glycemic foods.

At the end of the study all participants, regardless of diet, showed similar levels of reduction in waist circumference and abdominal fat mass. Both subcutaneous fat (that under the skin) and visceral fat (that surrounding the internal organs) was reduced similarly in both diet groups. Measurement of blood lipid profiles also showed that both groups exhibited improvement in the level of circulating triglycerides. The only significant differences in lipid profiles were that only the LFHC diet resulted in reductions in total cholesterol and low-density lipoprotein-associated cholesterol (LDLc: the so-called "bad cholesterol") and only the VHFLC diet resulted in increased HDL.

Both diets were associated with reductions in the level of insulin resistance and reduced levels of glycosylated hemoglobin, commonly identified as A1c. Although both diets resulted in these same metabolic improvements the VHFLC diet resulted in the changes after the first 8 weeks, whereas, the LFHC diet showed more rapid but gradual improvements.

So the TAKE HOME from this study for all you dieters out there is that consuming a diet where the energy used by the body comes primarily from carbohydrate or from fat does not result in differences in disease such as the metabolic syndrome. In other words a low fat diet that contain, overall, energy in excess of what you need is going to result in the same level of disease as a diet that is low carbohydrate but also of an energy content in excess of what you need. The real significant outcome from this study was that dietary fat, in and of itself, does not represent the underlying cause of accumulating central adiposity which is a precursor to cardiovascular disease and ultimately death.



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