Ultra-processed Foods and Weight Gain

There has long been a debate among nutrition and weight loss experts about calories. Some say that calories don’t matter – that 1000 calories of broccoli is the same as 1000 calories of ice cream when it comes to energy consumption by the body. Others will insist that the source of the calories is more important than the number consumed and that complex hormonal effects will determine a lot of how the body handles calories from different sources.

Both sides have legitimate arguments, which can get quite complex in terms of how the body handles different types of nutrients like sugar and fat, but recent research indicates that the big differences in weight gain between eating “junk” versus eating “healthy” are actually pretty simple.

A recent study put the same group of people on two different diets with basically the same calorie content and nutrient composition for two weeks on each diet to compare them. One diet was made up of ultra-processed foods – in other words, what most of us would call “junk food.” The other diet was comprised of minimally-processed foods – unprocessed meats, fresh produce, etc.. The test subjects were told to eat as much as they wanted of the food provided while on each diet.

At the end of the study, one major finding stood out – the test subjects consumed an average of about 500 calories more per day while on the ultra-processed diet than they did on the minimally processed diet, which of course led to weight gain.

There’s a couple of reasons for this. One is that ultra-processed foods are designed for “hyper-palatability.” In other words, they taste really good and cause the pleasure centers of the brain to be activated when consumed, making you want to consume more. The other reason is that ultra-processed foods can generally be eaten faster than minimally-processed foods and this leads to a tendency for eating to outpace the activation of the brain’s satiety centers that tell you when you’re full and to stop eating.

The speed factor is actually pretty significant. Take the example of meats. If you compare something like TV dinner meat loaf or processed, sliced deli meat, you generally don’t need to cut it into bite-sized pieces and it usually requires less chewing than something like a steak or a whole chicken breast. It usually takes significantly longer for you to eat minimally-processed food than ultra-processed, and this allows the satiety center of the brain to keep up and keep you from eating past the point of being full.

Speed of consumption is one of the “Three V’s” of the snack food industry: Value (cheap to buy), Variety (varying flavor profiles, such as different flavors of chips, maximizes consumption of the base product), and Velocity (speed at which it can be consumed).

As a side note, snacking really wasn’t a common part of most people’s dietary habits prior to 1970, when the food manufacturing industry sought to increase revenue and began to produce a wide variety of snack foods. It’s probably just a coincidence that obesity rates began to skyrocket right around that same time!

Getting back to the main point, calories are calories to a large extent, regardless of the source, but because of hyper-palatability and speed of consumption, ultra-processed foods typically lead to much higher consumption of their calories than those of minimally-processed foods.

These two factors probably have a lot to do with the success (at least short-term) of many popular weight-loss diets. Successful diets tend to have reduced flavor intensity and variety (remember the “Three V’s?), so eating is less-activating of the brain’s pleasure centers, and such diets often require longer time to consume the food, so your satiety center can more effectively tell you when to stop eating.

So, while a calorie is, for the most part, a calorie, sticking to food that is as minimally-processed as possible will most often allow you to lose weight (if needed) easier and to maintain a healthy weight. It also usually helps to switch to pre-1970 snacking habits – in other words, don’t snack (unless you have a health condition that necessitates it).

Until next time…

George F. Best, D.C.