Eating processed food leads to weight gain

From Tom Venuto from the Burn the Fat E-zine 

"Eating processed food leads to weight gain; eating unprocessed food leads to weight loss? Duh. Of course. Common sense. Not news." But there is new news about ultra-processed food, from a study just completed at the National Institutes of Health in Bethesda.

Common sense may dictate that "processed foods are fattening," but how? Are they simply a delivery vehicle for excess calories or are they inherently fattening in some other way as well? If this seems like an odd question, consider that it's not unusual at all for people to believe that refined sugar simply turns right into body fat (false).
 
Only a controlled study can show a cause-effect relationship between food and fat gain and that's what this study did - the first study of its kind. The scientists admitted 10 men and 10 women who were weight-stable into their inpatient facility where they lived for 28 days and everything they did could be controlled and measured.

They were assigned randomly to the ultra-processed or unprocessed diet for 2 weeks, and then crossed over to the other diet for 2 weeks. Each participant was given 3 daily meals and instructed to eat as much or as little of them as they wanted (ad libitum). The results?

On the ultra-processed diets, subjects ate on average, 508 more calories per day. That's an ENORMOUS difference. It shouldn't be a surprise then, that on the ultra-processed diet, subjects gained weight (1.7 lbs in only 2 weeks) and lost weight on the unprocessed diet (2.4 lbs in only 2 weeks).

Before shrugging this off as, "Still just common sense," a key point to remember is that the subjects were not counting calories or tracking macros. Also, if this is common sense, then why are there still so many diet wars with factions arguing, sometimes aggressively, about whether the ideal weight loss diet is low carbohydrate, keto, paleo, grain-free, high protein, low fat, vegetarian, vegan,  and so on?

The question is not whether these diets work - all of them can work, and no single diet is going to be suitable for everyone's preferences and lifestyles. The more important question is why do they work? For some strange reason, there are still large numbers of people who don't believe weight loss is a calorie thing. Low carb dogma is usually dismissive of the role of calories. Low carb and keto advocates to this day will tell you that obesity is caused by carbs and insulin (wrong).

It really is an excess of calories that leads to fat gain. Ultra processed carbs can simply be a big part of that energy surplus in the average person's diet, and the call to cut carbs is simply one way to reduce calories. Also kind of strange if there's no specific health reason for it, the "reduce carbs" guideline often includes non processed carbs like sweet potatoes, brown rice, beans, oatmeal, 100% whole grains, even, believe it or not, fruit.

In a similar fashion, all kinds of specific foods, from wheat to dairy to potatoes and more, have been demonized and implicated in fat gain by an endless parade of popular diets, with no cause and effect evidence. It's never advertised as "too many calories" because that's not sexy enough to sell.

Popular diet recommendations are diverse, but the ones that work all share a common piece of advice: avoid or minimize ultra-processed foods. The scientific evidence points to obesity and associated diseases like type 2 diabetes rising in parallel with an increasingly industrial food system and the easy availability of cheap processed food.

We may still be talking common sense here, but there were more "uncommon" findings that popped up in this study as well. Some previous research theorized that ultra processed foods are hyper-palatable, have "supernormal appetitive properties," or may disrupt gut-brain signaling and influence food reinforcement and overall calorie intake through pathways distinct from energy density or palatability of the food.

As many scientists have suspected, appetite hormones are involved. The high processed food group saw an increase in the hunger hormone ghrelin, while the unprocessed food group saw an increase in the appetite suppressing hormone PYY (peptide YY).

Yet another interesting finding was that the processed food group ate faster - 17 calories per minute faster. This eating rate was directly correlated to higher total calorie intake. Previous studies found that a 20% change in eating rate can impact energy intake by 10 to 13%.

And an even more notable finding for the few remaining who still don't believe in calories in vs calories out: This was a metabolic ward study, so calorie balance could be directly tracked. The amount of weight gain experienced by eating the processed food correlated highly with the amount of surplus calories consumed. This gives us more confirmation about the role of energy balance in weight gain or loss.

Like many pieces of the body transformation puzzle, this is simple stuff, but not easy to apply, especially when you consider how cheap, convenient and ubiquitous junk food is.  Be prepared to flex some discipline and put in some effort, because eating for healthy fat loss is not always easy in our modern environment.

"Eat less processed food" is sound advice, for health as well as weight loss, but it may not be useful enough to stop there. Meal planning and more specific strategies on controlling excess calories from processed food will help even more.