When is a calorie not a calorie?

Once you have to start counting calories, it takes away from the joy of eating.

Mireille Guiliano

I’m not a great one for diets, my weight does tend to fluctuate a little but I’m usually fairly good at getting trim again when I need to. All that said, I did read an article in a magazine this week that actually made a lot of sense!

Dr Giles Yeo, a geneticist at Cambridge University who has been researching obesity for more than 20 years, says that much of what we think we know about calories is wrong. “Calorie information is everywhere,” Yeo says. “But it’s all based on lousy science.” What matters, he says, is not how many calories a food contains, but how many of those calories are available for our body to absorb, which is known as a food’s “caloric availability”.

Yeo explains how it is not the number of calories listed on a label that matter when it comes to losing weight, but how our bodies use and store the calories from that food. He says that “caloric availability” is influenced by how a food is prepared and how we digest it and that the further away from its original state it is by the time it reaches your mouth, the more calories are readily available for your body to store.

It’s not just ultra-processed fast food and ready meals that should have a warning sign, but anything from chickpea flour and corn tortilla to green smoothies and kale chips. “To lose weight and stay healthy, what we should be looking at is not how many calories are in a food, but the quality of that item,” he says. “If it’s processed or altered in any way, then the body will absorb more of the calories it contains.”

The process used to estimate calories for food was developed at the turn of the 19th to 20th century by an agricultural chemist called Wilbur Atwater who burnt samples of food, then measured the amount of energy released from the heat they produced.

His simple system of calculating four calories for each gram of protein, nine calories for each gram of fat, and four calories for each gram of carbohydrate (modified later by others to add two calories for a gram of fibre) has been used ever since.

It resulted in one of the longest-standing truths of dieting — that the more calories we consume (and the fewer we expend), the fatter we will get. However, Yeo says this message is outdated. “While calories are a useful measurement, they are of very limited use when it comes to health and weight loss,” he says. “Calorie values are based on 120-year-old science and don’t take into account what happens to food when we eat and cook it.”

Everything from processing, cooking and reheating food to the diet-induced thermic effect of eating it — the energy or calories needed by the body to chew and break it down, synthesise enzymes and perform metabolic processes — influences how our bodies use and store the calories any food contains. “We need to forget label-checking for calorie counting and focus instead on the quality of a food and how wholesome it is,”

The article goes on to give some helpful tips and trips based on Yeo’s years of research. One of the things he advocates is losing weight by eating a plant-based diet two to four days a week. As a confirmed carnivore he admits the thought of it frightened the life out of him but he gave it a go. He found that in the space of a month he lost over four kilos!

Who knew but, cooking increases calories in all food! Yeo says that our ancestors, who had to hunt for food, invented cooking partly as a way to access as many calories as quickly as possible. “Whenever you cook a food, it increases the caloric availability of it — in other words, your body takes more calories from that food than it would from the same food in its raw state,” he says.

“This is because the process of cooking does some of the work usually performed by our stomach, making it more easily digestible.” Sometimes a cooked food provides as much as five times more calories than the uncooked version. An extreme example is a stick of celery, which when raw contains about six calories. Put that same stick of celery in a stew and you increase its caloric availability to about thirty.

“All foods experience calorie changes when cooked just to differing degrees,” Yeo says. “But it is always an increase in calories available to the body.” He says that trying to eat as many vegetables raw, stir-fried or lightly steamed as you can will reduce this additional energy intake.

Another thing I didn’t know was, beef is higher in calories when it’s minced than it is as a rare steak, again, who knew!! For health reasons, Yeo suggests cutting down on red meat (and cutting out processed meat altogether), but if you do eat some it should be no more than twice a week and you should choose whole cuts that can be quickly cooked, such as steak, to aid weight loss.

Pound for pound, minced beef and steak might contain the same number of calories when raw, but not when they are on your plate. “Mincing meat and then the process of cooking it alters the collagen protein it contains, making it easier to chew and digest,” Yeo says.

Yeo goes on to talk about why we should eat fruit and avoid smoothies. Calories absorbed from any fruit are multiplied several-fold when it is juiced or pulped into a smoothie, (OMG – I’ve been drinking loads of smoothies in the hot weather because I thought they were healthy!). “If you eat an orange, you need to chew it first, using muscles of the jaw and mouth, and then your body needs to fight through the fibre it contains to digest the fruit,” Yeo says. “Then there is additional energy involved in pooping it out the other side, meaning the whole process is hard work for the body.”

By comparison, drinking juiced or pulped orange juice does not required much effort. “There’s no chewing, no energy used to consume it,” Yeo says. “Digestion is minimal, meaning a juiced fruit almost immediately enters the bloodstream, providing a greater number of calories and raising blood sugar.”

There’s tons more stuff but one thing that jumped out at me was the fact you shouldn’t cut all the Carbs out of your diet such as in the Keto diet. Cutting all carbs out of your diet is not necessary for weight loss. “Yes, refined carbs should go, but losing wholegrain carbs completely makes it difficult to get enough fibre, which plays a role in leaving you satiated,” Yeo says. “You can get fibre from fruit and vegetables with very few added carbs, but fibre from wholegrain continues to be an important source.”

He says we should look for wholegrain versions of all carbs as the thermic effect of eating them — all the chewing and digesting — can be almost double that of processed versions of the same food. To demonstrate this, researchers from Pomona College in California looked at two ready-made sandwiches, one containing traditional cheddar cheese in multigrain bread, containing wholegrain kernels and sunflower seeds, and another made with white bread and Dairylea or Kraft-type processed cheese.

On paper, both sandwiches contained the same number of calories and a similar proportion of carbohydrate, protein and fats. Yet the researchers showed that the participants who ate the processed sandwich meal saw metabolic rates drop below their average basal metabolic rate — the basic energy needed to keep you functioning at rest — during the sixth hour after eating, which didn’t occur with the wholegrain group, but that they also absorbed more calories.

“In that trial participants had to spend nearly twice the number of calories to metabolise the wholegrain sandwich compared to the processed version,” Yeo says. “Put another way, eating the processed sandwich means you absorb 10 per cent more calories than if you had eaten the wholefood sandwich. And those calories will head to your waistline.”

Apparently, he’s just had a book published; Why Calories Don't Count: How We Got the Science of Weight Loss Wrong, you know what, I may just buy it!

What’s on this week?