Why consumption of ultra-processed food leads to weight gain

​I have always thought that eating raw food is better for us, and this study by Kevin D Hall et al proves this.  Their study concludes that an average person eating ultra-processed food puts on almost 1kg in 2 weeks while eating unprocessed food leads to the same weight loss in the 2 weeks.  And this is huge. So how did they do this?

They looked at 10 women and 10 men and observed them up in a very controlled environment.  They randomised them into 2 groups.  One was eating unprocessed food for the first 2 weeks then swapped to ultra-processed food for the send 2 weeks.  The second group started with 2 weeks of ultra-processed food and they swapped them to unprocessed food for the 2 weeks after.  But it did not matter which group they belonged, the results were similar.

When people were eating ultra-processed food they were:

• Consuming more calories per meal  (500-600 kcal per day more)

• They have eaten more fat and carbohydrate, but a similar amount of protein

• They were eating faster on average than when they were eating unprocessed food.

• Unprocessed food was more expensive ultra-processed food.

During the 2 weeks that they were on ultra-processed food, they put on average just under 1 kg in weight.  Most of that gained weight was a combination of fat mass and fat-free mass.  During the 2 weeks on an unprocessed food diet, they lost on average just under 1 kg in weight. 

Why was this:

• the appetite-suppressing hormone was in higher levels during the unprocessed food diet then ultra-processed

• total cholesterol was higher in those eating ultra-processed diet, but this was mostly from HDL ("good cholesterol").  They did not measure the ratio that is more important, but if I did it, I assume that there would not be significant differences.

• There was no difference in oral glucose tolerance (or insulin resistance) during these 2 periods.  This could be because everyone was exercising and this may have lowered the levels.

To me, it would be interesting to find out what would happen if we/they were consuming unprocessed diet for longer?

So, in conclusion, people who eat ultra-processed diet are likely to consume more calories and become overweight than those people who consume unprocessed diet.  But the ultra-processed diet is cheaper.
We/governments need to increase the price of the ultra-processed food and decrease the price of unprocessed food so everyone has an easier choice to eat healthier food, not just people who can afford it.