It’s a nutrition “truth” universally acknowledged: We should avoid ultra-processed foods. Even diets deeply at odds over other things — what percentage of carbs, fat or protein we should eat or whether grains, dairy or meat enhance health or harm it — agree that ultra-processed foods contribute to poor health. But how do we know that for sure?
My ears pricked up a few years ago when I heard National Institutes of Health researcher Kevin Hall mention a study he was planning to get to the bottom of that very question. The research, published online last month, found that a diet composed primarily of ultra-processed foods does in fact lead to increased calorie intake and weight gain, as well as some undesirable changes in fasting blood sugar and cholesterol — but not for the reason you might think. Forget hyperpalatability and the “bliss point” conjured up by some magical ratio between salt, sugar and fat. The story can’t be wrapped up that neatly.
What research found
In this study, 10 men and 10 women were randomly assigned to eat an ultra-processed or unprocessed diet for two weeks in an inpatient setting, then switch. Ultra-processed foods are created in factories, generally from components extracted from whole foods rather than from whole foods themselves, and contain chemical additives to enhance color, flavor, texture and shelf-life.
Think frozen pizza, snack foods, breakfast cereals. Unprocessed and minimally processed foods include things like apples and broccoli, as well as canned tuna and plain yogurt.
The two diets as offered were virtually identical in calories, sugar, fat and fiber. The ultra-processed diet was a shade lower in protein and higher in carbohydrates, but had a similar glycemic index.
Participants were allowed to eat as much, or as little, as they wanted — which translated to 500 calories more per day when they were eating the ultra-processed diet. This led to about 1 pound of weight gain on the ultra-processed diet, and about 1 pound of weight loss on the unprocessed diet.
So why did the ultra-processed diet cause people to eat more? Again, it’s not what you think. All participants had the chance to follow both diets, so it’s not that people with larger appetites or greater calorie needs just happened to be assigned to the ultra-processed diet.
In fact, participants rated their hunger, fullness, satisfaction and eating capacity almost identically on both diets — even though levels of an appetite-suppressing hormone were higher on the unprocessed diet, and levels of the “hunger hormone” ghrelin were lower — and both diets had similar scores for familiarity and pleasantness.
One notable difference was that people ate the ultra-processed food faster, to the tune of an additional 17 calories per minute. The researchers speculate that it may have been easier to chew and swallow. Also, the ultra-processed food itself was more calorie-dense, although the diet was not once you factored in the beverages that served as vehicles for dissolved fiber supplements.
Almost more interesting than the study itself was the ensuing discussion on social media — including free-flowing opinions from people who didn’t appear to have read the actual research. Some clung to the idea of hyperpalatability, while others expressed unfortunate stereotypes about the “type” of people who eat a lot of ultra-processed foods — the word “gluttony” was tossed around quite a bit — and evoked the ever-present edict of personal responsibility, which glosses over deeper issues surrounding nutrition and health.
This study raises more questions than it answers, as good science often does. You might think that the solutions are clear — people need to cook more, and the government needs to tax ultra-processed foods. In fact, they are not that obvious.
Easier said than done
I’m a fan of cooking from scratch. I have a well-stocked pantry, freezer and fridge, roughly 300 cookbooks, and the tools and confidence to make pretty much anything that strikes my fancy. But despite those tremendous resources, sometimes dinner is frozen breaded chicken cutlets heated and served over bagged salad mix (the kind that comes with its own dressing), because life happens.
Imagine then, the single parent who is juggling multiple part-time jobs. Or doesn’t know from week to week what their work schedule will be, making meal planning a pipe dream. Or is lucky to afford ramen and cheap hot dogs the week before payday — forget having extra funds to stock up on food staples when they’re on sale. (Please stop before you say, “But dried beans and rice are cheap.”)
I have clients who can easily afford fresh, local, organic, sustainable produce, but find getting a home-cooked meal on the table challenging on weekdays. Sure, they could do advance prep on the weekend, something I often recommend, but what would you do if you couldn’t afford a cutting board and a sharp knife?
I love Michael Pollan’s “In Defense of Food,” but I think everyone who reads it should also read “Pressure Cooker: Why Home Cooking Won’t Solve Our Problems” by sociologists Sarah Bowen, Joslyn Brenton and Sinikka Elliot. That will open your eyes to reality.
So before we endorse taxing someone’s cheap frozen pizza — that may be the only thing they can afford that they know their kids will eat — before we assume that people who eat ultra-processed foods are lazy and don’t care about their health, we need to check our privilege.
As Hall and his co-authors point out, ultra-processed foods are less expensive and more convenient than preparing meals using unprocessed whole foods and culinary ingredients, or more pointedly, that “policies that discourage consumption of ultra-processed foods should be sensitive to the time, skill, expense and effort required to prepare meals from minimally processed foods — resources that are often in short supply for those who are not members of the upper socioeconomic classes.”
Next week, I’ll offer tips for reducing ultra — processed food intake that are a little less idealistic and a little more real.