Calorie counting can be a nightmare if you're trying to lose weight, so the ability to simply avoid an extra 500 calories daily would come as a relief to many slimmers.
Professor Tim Spector shared the handy way to dodge hundreds of calories on a recent episode of Michael Mosley's Just One Thing podcast.
Introduced as a "leading expert" on nutrition by the diet guru, Professor Spector went on to explain how one type of food can increase your appetite, leading people to hoover up an extra 500 calories a day.
The Kings College epidemiologist says his top food tip is to reduce or avoid ultra-processed food. According to Prof Spector, the fat, sugar and salt content of food isn't the only important thing in our diet - it's how food is processed.
What are ultra-processed foods? While there isn't a universal definition, he says 95 percent of these foods are "dead easy" to spot.
Dubbed "fake foods" by the scientist, he says the easiest thing to do is to look at food labels and recognise what's not in your kitchen. It may come as a surprise that wholesome everyday items like bread and muesli fall under the banner of ultra-processed foods.
The nutrition expert says not only are they not good for your gut health, they're bad for the waistline as it increases your appetite.
He told Michael: "I think the key thing people don't realise is, as well as affecting your gut health, recent studies have shown that it increases your appetite."
When compared to home cooked food, Professor Spector said you could eat the same amount of calories of ultra-processed food and end up consuming an extra 500 calories a day.
"Eating identical calorie meals - one home cooked the other processed - equally tasty, you will eat an extra 500 calories a day of ultra-processed food," Prof Spector pointed out.
"It will make you feel rotten and you don't know why cause you've read the packet and it says it's low calorie and low fat."
According to Professor Spector, ultra-processed foods make up 57 percent of the British diet - a number that jumps to 70 percent for children.
The nutrition expert recommends his diet regime eating 30 plants a week. Check out our explainer of the veg heavy diet of which Prof Spector says: "If you could eat 30 plants a week, pretty much you solve 90 percent of your problems."
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