Fat + sugar = metabolic derangement

A recent study of interest in the International Journal of Obesity explores whether problems with glucose metabolism (aka metabolic syndrome) are related to obesity (and hence the chemical properties of adipose [fat] tissue) and/or the diet itself.

The effects of the diet may be related to the digestion of the food (i.e. the pancreas having to deal with the sugar load, etc.), but interestingly, they can also be related to the way the brain and appetite hormones process the food. So basically we’re asking: How does a poor diet screw us up? Is it:

  • the way our bodies react when they are or become over-fat?
  • the way our bodies must digest and process the food itself?
  • the way our brains and hormones respond?

Of course, it’s probably all of the above.

Then we want to ask ourselves: What does “poor diet” really mean? High fat? High sugar? High fat and sugar? Well, as it turns out, fat+sugar (in other words, the vast majority of shitty fast food) may be the magical metabolic bomb that explodes our insides.

Researchers exposed rats to 4 different types of diets:

  1. high saturated fat (beef tallow);
  2. high sugar (sucrose solution);
  3. high fat and sugar; and
  4. a control diet of regular rat chow.

What happened? Well, all the rats who weren’t on normal diets got fat. That’s not surprising. Fat and sugar are both very tasty, even to rats, so it’s not hard to pack on the pounds either way.

In addition, high-fat (HF) and high-fat/high-sugar (HFHS) diets both raised blood lipids (aka plasma concentrations of free fatty acids). However: only rats on a free-choice HFHS diet developed hyperglycemia, hyperinsulinemia, glucose intolerance and a diminished insulin response to a glucose load. The HF rats were corpulent, lardy-arteried little buggers too… but didn’t have all the other metabolic derangement.

Moreover, although the high-sugar rats showed elevated insulin (hyperinsulinemia) along with more body fat , their blood sugar levels and glucose tolerance were not different than the controls, suggesting that sugar alone is not responsible for the observed glucose intolerance.

Therefore, concluded the researchers, it’s not fat or sugar alone that’s the issue — it’s fat and sugar together.

Consider this the next time you eat a donut.

S E la Fleur, et al. A free-choice high-fat high-sugar diet induces glucose intolerance and insulin unresponsiveness to a glucose load not explained by obesity. International Journal of Obesity (2011) 35, 595–604; doi:10.1038/ijo.2010.164; published online 17 August 2010