The case for a wholefoods diet for weight management

The case for a wholefoods diet for weight management

What if you ate two different diets carefully matched to provide the same amounts of calories, sugar, fat, fibre and macronutrients?

One diet ultra-processed, like on the left in the picture above. And the other diet unprocessed, like on the right.

What would it do for weight management? This is exactly what Dr Kevin Hall, PhD tested in a study published in Cell Metabolism on 16th May 2019.

And it provides evidence and insights for how to better sell people on the idea of eating well. 

What they did

Twenty inpatient participants received all their meals and snacks from either an ultra-processed or unprocessed diet for 14 days each. The diet option was randomised and then swapped for another 14 days.

Participants were allowed to eat as little or as much as they liked from the diets that were matched for presented calories, sugar, fat, fibre, and macronutrients.

Only the form was different. For example, a breakfast for the ultra-processed diet included a bagel with cream cheese and turkey bacon. An unprocessed breakfast included oatmeal, bananas, walnuts and skim milk. See photos of the full menu here.

What happened?

When presented with the ultra-processed diet, study participants ate on average 500 calories per day more and gained weight (about a pound per week) with the increased calories.

This finding by itself (I call the `why') should be enough to convince people to ditch ultra-processed foods. But it often helps to understand the mechanisms (the `how') to build a stronger case to eat well.

Selling the case for wholefoods

Kevin Hall and his team presented possible reasons why the ultra-processed diet was more fattening. I've presented them below with selling points (aka a marketing pitch) for making the switch to a nutrient-rich whole foods diet for weight management.

Whole foods take longer to eat

Individuals ate much faster on the ultra-processed diet, consuming 17 more calories per minute compared to the unprocessed diet, perhaps due to the ultra-processed foods being softer food that was easier to chew and swallow.

The sales pitch

Eating whole foods can slow down eating to give your brain a chance to register that you are full. Eating ultra-processed foods speeds up your eating and calorie intake.

Whole foods are more satiating

Even though people didn't subjectively rate appetite scores differently between the diets, the appetite-suppressing hormone PYY increased during the unprocessed diet. And, the hunger hormone ghrelin was decreased during the unprocessed diet compared to baseline.

The sales pitch

Whole foods help your appetite hormones work better. Ultra-processed foods, particularly drinks may not trigger your appetite hormones causing you to automatically consume more.

And here are some additional selling points for whole foods.

Whole foods cost more energy to digest

In a study comparing the postprandial thermogenic responses (increase in metabolic rate) to a whole food cheese sandwich meal versus a processed cheese sandwich meal, researchers discovered that energy expenditure from the whole foods meal was almost double that, 19% of meal energy versus 10% of meal energy for the processed meal.

The Hall study did find that 24-hour energy expenditure was greater for the ultra-processed diet compared to the unprocessed diet but suggested this was due to the energy cost of processing the larger calorie intake.

The sales pitch

You end up getting fewer calories from whole foods because they cost more energy to digest and process. For ultra-processed foods, more of the calories can end up in your body.

Whole foods can improve your mood and reduce depression

According to a meta-analysis published in April 2019 covering 16 studies with over 45,000 study participants, dietary interventions to improve eating significantly reduced depressive symptoms.

A range of ingredients in whole foods were suggested as being benefical;
Fruits and vegetables with polyphenol antioxidants with anti-inflammatory, neuroprotective, and prebiotic properties.

B vitamins, omega 3 fatty acids, minerals (e.g. zinc, magnesium) and fibre (e.g. resistant starch) as well as other bioactive components (e.g. probiotics), may also be protective for mental illness.

The authors concluded that the review...

"strongly suggests that diet can play a role in the treatment and also self-management of depressive symptoms across the population."

The sales pitch

Whole foods nourish your body and mind to improve mood. An ultra-processed diet can contribute to poorer mood.

Whole foods have less food chemicals that can damage gut health

Increasingly, scientific evidence is suggesting that the health of your gut has an influence on risk of chronic cellular inflammation and various health conditions.

For example, in May 2019 researchers at the University of Sydney found in rats...

“that consumption of food containing E171 has an impact on the gut microbiota (defined by the trillions of bacteria that inhabit the gut) which could trigger diseases such as inflammatory bowel diseases and colorectal cancer.”

E171 are titanium dioxide nanoparticles that are a whitening ingredient in more than 900 food products, including in the garlic aioli on McDonald's classic grilled chicken burger.

Questions also surround the impact on the health of intestinal gut lining by other processing ingredients like emulsifiers and thickeners.

The sales pitch

Whole foods keep your gut and metabolic functions healthy. Ultra-processed foods may contain ingredients that harm your gut and metabolic health.

It's no longer just about calories

What the Hall study did so well, was to show that eating for weight management is not just about calories. There are so many more reasons to make the switch from an ultra-processed diet to eating a nutrient-rich whole foods diet.

And as the evidence builds, there are a growing number of ways to sell the idea to people. 


The End of Ultra-Processed Foods? Recorded Webinar

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