Tuesday, August 18, 2009

Eating Processed Food Makes It Easier To Gain Weight

Evidence for the harm caused by eating processed food - food made from overly processed grain (flour) with added fats and sweeteners - is mounting.

Can just changing the texture of food, processing it, contribute to weight gain?

That was the question Kyoko Oka, et al. asked in:
Food Texture Differences Affect Energy Metabolism In Rats, 2003

Two groups of rats were fed either standard pellets or easily-chewed, soft pellets (made softer by increasing air content, as is done in breakfast cereals).
  • Calorie intake was measured to be the same in both groups.
  • Nutritional composition of diet was the same in both groups.
  • Meal duration was the same in both groups.
  • Calorie expenditure via locomotion was measured to be the same in both groups.
If energy intake, nutrient intake, and energy expenditure (activity) are similar, you would expect body weight and body fat to be similar. That wasn't the case.

  • After 18 weeks and beyond, "body weight in the soft-fed group was significantly greater."
  • After 22 weeks the rats were dissected. Weight of abdominal fat in the soft-fed group was significantly greater, enough to designate the rats as obese.
  • The increased body weight in the soft-fed rats was due to increased body fat.
The authors concluded:
"In this study, 22 weeks was long enough to produce obesity in soft-fed rats." (They ate the same number of calories.)


The cost for digestion in the soft-fed rats was lower. This cost was measured in body temperature, which was significantly lower in the soft-fed group after a meal (up to 1 hour). Body temperature (thus, energy expenditure) was also significantly lower in the soft-fed group "during the dark period" or overnight.

If weight loss and reduction of body fat are the goal, merely reducing the number of calories consumed won't be as effective as also reducing the amount of processed food consumed, e.g. bread, crackers, breakfast cereals, and baked goods.
Idea thanks to Richard Wrangham and his book Catching Fire. Great book.


Perovskia said...

Sure... if food is softer, it's more pleasing to the palate, thus we'll eat more.

It makes me sad we have to increasingly inject fats and sweeteners into our foods to make them more appealing.

It kind of makes me think of WALL-E. Have you seen that movie? It makes a very real projection about what our society will be like in x-amount of years (I thought it was brilliant). Although it has other factors that come into play, food for them is *so* readily available that they become this obese nation. They're not far off....

Bix said...

They didn't eat more in this study. They ate the same number of calories.

Perovskia said...

I apologize. I retract my first paragraph.

Bix said...

No need to apologize. You're right about comfort/emotional eating.

I found the mechanism fascinating. It's one more example that challenges the conventional thinking that all calories act the same.

Anrosh said...

growing up we would get to eat bread ( white bread.) with jam only on sunday - 4 pieces were allowed with half a glass of milk. because my mom needed a break one day of the week. i must confess i loved white bread then.

who knew that flat bread made out of 100 % whole wheat that we had 6 days of the week was healthy?
it was by default.

Perovskia, lots of info on your blog but cannot post a comment because it has an embedded form.

Perovskia said...

Bix... I was once told, "A calorie, is a calorie, is a calorie". Ha, for some reason that didn't sit right with me.

Anrosh... so sorry. You were able to post before. What do you mean embedded? (Sorry, still learning.) Tell me how to fix it and I will :)

Family Nutritionist said...

Blood sugar spikes have profound effects on metabolism and fat storage.

Softer food is digested faster, so the macronutrients get into the blood faster.

Blood sugar and insulin spikes leading to preferential storage of available calories as fat is another possible mechanism.

Maybe their triglycerides and CRP were worse, too.