Repost: Eating Processed Food Makes It Easier To Gain Weight

This is a repost from 2009. I think foods that are soft and air-entrained would fall into this category ... breakfast cereals, soft white bread, crackers, cookies, cake. Maybe you can think of more. That they could eat the same number of calories and have different outcomes surprised me.
________ 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.

Findings

• 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.)

Mechanism

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.