Do High Fat Diets Make a Person Tired and Dumb?

A new study by Oxford researchers has shown one way that a high fat diet¹ challenges your body's health, leading to a decline in energy and mental function within nine days.

Even a short-term high fat diet (55% of calories as fat – typical junk food diet) can reduce energetic capacity and endurance, while at the same time impairing mental capability. Not exactly a competitive advantage in sports or in the office.

A specific mechanism was identified – an increase in uncoupling proteins. This means that instead of using calories to produce energy, normal metabolism was uncoupled by the high fat diet so that the extra calories could be disposed of as heat. This is a defense mechanism against being poisoned by too much food.

The trade off, in order to perform this defensive action, is that normal energy production is sacrificed. This resulted in a 50% drop in endurance by the 9th day (animal study).

Since the energy currency of your body (ATP) is also used by your brain as a communication molecule, it is not at all surprising that less physical energy would coincide with less mental horsepower and ability.

If you want you brain and body to have a fighting chance, don't poison yourself with too much food. I found this study interesting, as any time I see myself eating more than I know I should it is obvious that I have less energy when I run.