A few years ago I was asked to comment on an experiment a young reporter on a news show did. He went on a diet of his own design to prove that "energy in v energy out" was all anyone needed to worry about to lose weight. His plan: pies and beer. Nothing, in fact, but a restricted number of pies and beers, every day for a month.
You can probably guess the result. Yes, he lost weight. Despite the content of the diet, his energy intake was restricted. Also, the appeal of the pies quickly wore off - by the end he wasn't eating very many.
So weight loss was achieved. Great, right? Did the reporter want to keep going with his brilliant diet plan? No, of course not. He felt terrible. This typical, pie-and-beer-loving young guy couldn't wait to get his face into a bowl of salad.
This is a demonstration of something every nutrition expert agrees about: quality matters. For optimum health, we need to focus on the quality of our diet, as much as or more than we need to focus on quantity. A pie is not the same as a pumpkin. The ideal healthy diet has more whole foods, fewer foods that are processed.
A recent study has reinforced this, and has pointed to the contribution ultra-processed foods may have made to the obesity epidemic over the years.
In the research published in Cell Metabolism, researchers tried the first randomised controlled trial to directly compare what happens when people eat unprocessed versus "ultra processed" foods.
They measured the differences in calorie consumption and weight gain between two groups of people who ate the ultra-processed diet (full of refined carbs, saturated fat and added sugar) and an unprocessed diet (full of whole foods) for two weeks each. This was a crossover trial, meaning the subjects did one diet, and then switched to the other one for the second fortnight. The researchers supplied all the food.
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The study found that even when the two diets offered to subjects were matched for carbohydrates, fat, sugar, salt and calories, people consumed more food, and gained more weight, on an ultra-processed diet. The opposite happened on the unprocessed diet.
One interesting suggestion from the researchers about why this is, has to do with protein. The ultra-processed diet was a tad lower in protein, yet subjects ended up eating almost exactly the same amount of protein in the end (they could eat as much as they wanted from the food supplied).
This suggests what's known as protein leverage might come into play: we keep eating until we hit a satisfying amount of protein, and if what we eat to achieve that is poor-quality processed food, the results are not great.
This makes sense, right? Low-quality, highly processed foods don't satisfy us. We tend to eat more as a result. Do that over a long period of time, and weight can creep up, and other poor health conditions can creep in.
Which all comes back to a simple out-take: eat whole.
• Niki Bezzant is editor-at-large for Healthy Food Guide; www.healthyfood.com