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HIGH FAT DIETS LOWER ENDURANCE

Posted Nov 04 2009 10:05pm

By Marie Dufour, RD – TAKE IT FROM THE RATS…. High-fat diets have long been known to lead to obesity, diabetes and heart failure and to be associated with cognitive decline in the long run.  But what is their short-term effect?

Oxford researchers switched rats from a regular diet (7.5% fat) to a high-fat diet (55% of calories from fat) and had them run on a treadmill.  Within just 9 days, the rats showed a 50% reduction in physical endurance, some metabolic changes, an enlarged heart, and a decline in cognitive ability. 

- Decreased performance: metabolically speaking, glucose is the preferred fuel for muscle work.  Since the body is a very efficient machine, it takes glucose from the most easily accessible source of glucose: carbohydrates.  Using fuel from fat is less efficient and, as the Oxford researchers discovered, causes metabolic changes.

- Metabolic changes: the rats exhibited increased levels of an uncoupling protein in their heart and muscle cells. This protein specifically reduces the efficiency of the heart and muscles.

- Enlarged heart: since the heart efficiency was reduced, it had to work harder and pump more blood to get oxygen to the muscles, quickly growing larger. 

- Cognitive decline: glucose is also the unique fuel source for brain work.  After 9 days on the high-fat diet, the rats starting having difficulties selecting their path in their usual maze, making more mistakes.

Now, some could say that even the gym rat in us is human and does not compare to a lab rat, and some might go on endorsing high-fat diets.  It certainly is the case at my gym where I see my trainers and body builders scarf down a breakfast of eggs, bacon and sausage, a lunch of hot dogs (no bun) and ham & cheese sandwiches (double-ham, half the bread), a snack of cake butter-frosting with whole-milk protein shake, and a dinner of burgers & ribs.  “High-protein, low carb, baby!”   and I wonder what will happen to their running performance, their heart and their minds. 

The Oxford study suggests that, contrary to previously thought, the harmful effects of high-fat diets manifest themselves in a short run.  It would be wise, then, for athletes concerned about peak performance, to watch their diets and select carbohydrates rather than fat as their fuel source… pretty quickly!

 

Ref: ‘Deterioration of physical performance and cognitive function in rats with short-term high-fat feeding’ by Andrew J Murray and colleagues is published online in the FASEB Journal. Copy of the paper: http://www.fasebj.org/cgi/rapidpdf/fj.09-139691v1.pdf.

Filed under: Lifestyle, diet, athlete endurance, athletic performance, Atkins, cognitive decline, diet, enlarged heart, exercise, healthy eating, healthy lifestyle, heart health, high fat diet, high protein diet, low-carb diet, Marie Dufour RD, obesity, sports nutrition, uncoupling protein, weight control, workout

By Marie Dufour, RD – TAKE IT FROM THE RATS…. High-fat diets have long been known to lead to obesity, diabetes and heart failure and to be associated with cognitive decline in the long run.  But what is their short-term effect?

Oxford researchers switched rats from a regular diet (7.5% fat) to a high-fat diet (55% of calories from fat) and had them run on a treadmill.  Within just 9 days, the rats showed a 50% reduction in physical endurance, some metabolic changes, an enlarged heart, and a decline in cognitive ability. 

- Decreased performance: metabolically speaking, glucose is the preferred fuel for muscle work.  Since the body is a very efficient machine, it takes glucose from the most easily accessible source of glucose: carbohydrates.  Using fuel from fat is less efficient and, as the Oxford researchers discovered, causes metabolic changes.

- Metabolic changes: the rats exhibited increased levels of an uncoupling protein in their heart and muscle cells. This protein specifically reduces the efficiency of the heart and muscles.

- Enlarged heart: since the heart efficiency was reduced, it had to work harder and pump more blood to get oxygen to the muscles, quickly growing larger. 

- Cognitive decline: glucose is also the unique fuel source for brain work.  After 9 days on the high-fat diet, the rats starting having difficulties selecting their path in their usual maze, making more mistakes.

Now, some could say that even the gym rat in us is human and does not compare to a lab rat, and some might go on endorsing high-fat diets.  It certainly is the case at my gym where I see my trainers and body builders scarf down a breakfast of eggs, bacon and sausage, a lunch of hot dogs (no bun) and ham & cheese sandwiches (double-ham, half the bread), a snack of cake butter-frosting with whole-milk protein shake, and a dinner of burgers & ribs.  “High-protein, low carb, baby!”   and I wonder what will happen to their running performance, their heart and their minds. 

The Oxford study suggests that, contrary to previously thought, the harmful effects of high-fat diets manifest themselves in a short run.  It would be wise, then, for athletes concerned about peak performance, to watch their diets and select carbohydrates rather than fat as their fuel source… pretty quickly!

 

Ref: ‘Deterioration of physical performance and cognitive function in rats with short-term high-fat feeding’ by Andrew J Murray and colleagues is published online in the FASEB Journal. Copy of the paper: http://www.fasebj.org/cgi/rapidpdf/fj.09-139691v1.pdf.

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