Over a century ago, Dr. William Howard Hay proposed that meals heavy in proteins and carbohydrates upset the digestive system and lead to weight gain.
The Hay (food combining) Diet still has loyal followers today – I’ve heard it mentioned by a couple of alternative doctors — but food scientists say separating proteins from carbohydrates has no credibility. The stomach is well equipped to handle any combination of proteins, fats and carbs.
I’ve generally agreed with them, for no very good reason except that eating all your protein at one meal and all your carbs at another sounds like a nuisance and not likely to be helpful.
But maybe I need to rethink the possible dangers of food-combining, because new research shows there’s a particular combination of macronutrients that will lead to weight gain. . .
These food combos that make you fat aren’t high in protein and carbs. They’re high in fat and carbs. The problem this combo causes is not related to digestion; it occurs because this combination plays havoc with reward centers in the brain.
Foods High in Fat & Carbs Preferred
A team of eight scientists from the United States, Canada, Germany and Switzerland recruited 206 adults for an unusual study in which the volunteers were allocated a limited sum of money to use to play a computer game.
They were shown photographs of well-known snack foods consisting mainly of either sugar, fat, or a combination of both. They were then asked to make a bid for the snacks of their choice.
While this was in progress, the researchers recorded their brain activity.
Not only were the volunteers more eager to pay greater sums for foods that combined fat with carbs, but the reward centers in the brain lit up more for snacks of this type rather than ones that were purely sweet or purely fatty.
This happened despite the fact that the people taking part had a stronger preference for foods higher in sugar or fat, the portion size was bigger and these snacks were more energy dense.
The fat-carbohydrate combination bypassed the normal responses regulating what and how much to eat. Instead, the brain was tricked into believing it was getting food of greater nutritional value than it actually was.
Senior author Dana Small, professor of psychiatry at Yale, said fatty and sugary foods each have a separate pathway of signals to reward centers in the brain, but “when the signals are combined they make foods more reinforcing.”
This reward response promotes overeating and therefore, the authors write, “facilitates the transition to habitual responding as is observed in drugs of abuse.”
The researchers said high fat/carb combinations are rare in nature, coming together only in breast milk, where the combo is rewarded because it is so vital for survival.
Even so, breast milk is only 3½% fat and 7% carbohydrate, whereas a typical ultra-processed snack is 24% fat and 57% carbohydrate. And today these are available in abundance.
Not Evolved to Eat Modern Foods
Opportunities to eat foods higher in fats and carbohydrates expanded with the agricultural revolution 12,000 years ago, but this is a short moment in time compared to the entire history of the human race.
We haven’t had time to develop accurate brain responses, particularly to the levels found in modern processed products of the food industry like pizzas, burgers, donuts, potato chips, french fries, and chocolate bars. Nor can we estimate the calories in these products – something we can do quite accurately for fats alone.
Marc Tittgemeyer from the Max Planck Institute for Metabolism Research, Cologne, Germany, said, “We are not meant to say no all the time. That’s why we usually do not stop eating, even though we’re full.”
So don’t blame yourself if you’re tempted to munch a second, third or fourth cookie. The only way to avoid the brain-stimulating and obesity-promoting effects of these products is not to eat them in the first place.
My favorite ploy is to simply not have them in the house. That way they’re not available when temptation strikes. If ice cream or pastries are around, I have a way of eating them.