Scientists say burned fat isn’t converted into energy — here’s where it goes
Most of us have been told when someone loses weight, their fat is “burned off” or turns into energy. But two experts say what we think we know about fat loss is completely wrong.
Writing a followup piece in The Conversation last week to their 2014 study about losing fat, assistant scientists Ruben Meerman and Andrew Brown of the University of New South Wales, said fat is converted to carbon dioxide and water, which we either exhale, urinate or sweat out.
Speaking with Global News, Meerman says when we exhale carbon atoms, they have to come from a source.
“They come from your most recent meal, but if you stop eating, they come from fat. If you put less carbon atoms back into your body than you exhale, you lose weight. If you put in more, you gain weight,” he says via email.
He says he decided to do a followup on his older study because the topic is still causing confusion among professionals and consumers.
He adds health professionals (his research surveyed 150 doctors, dietitians and personal trainers), still have the mindset that fat is converted into energy. In his 2014 research, only three survey respondents gave the right answer, he adds.
“I am still working on how we can improve this gap in the health literacy of students at every level of the education system,” he says. “I’m currently working on a community health education/literacy project will all the residents of a medium-sized community… that their bodies are made of the atoms that they ate, and that they exhale all of the carbon atoms in macronutrients.”
But registered dietitian Desiree Nielsen of Vancouver says while this study is a clever way to look at human biochemistry, fat can still create energy.
“When our fat cells release lipids, they are in fact used to create energy in the body,” she tells Global News. “So while yes, it is true that fat doesn’t transform into energy… it is the transformation of fat into carbon dioxide that creates energy.”
She says when our bodies give the signal that it needs more energy, lipase in fat cells helps release the fat into circulation.
“Once that happens, fatty acids are gobbled up by cells hungry for energy, like our muscles, where it can be used immediately or stored in droplets for later. To create energy, the fatty acids enter the mitochondria — the energy factories of our cells — where they are converted into carbon dioxide, heat and water, making something called ATP in the process,” she continues. “It is ATP that is the energy currency of the cell.”
Looking at diet
And we all know some fat from our diet is directly related to weight gain, but Nielsen notes it’s a lot more complex than just this. She adds health professionals used to say energy balance or weight maintenance was all about calories in and calories out.
“In theory, you could gain weight if you ate too many bananas or lose weight under-eating ice cream. However, the metabolic effects of the foods we eat play a large role in determining how much energy we are going to take in, and whether or not we store or release fat.”
She continues, dietary fat, for example, has more than double the energy density of carbohydrates or protein, but it doesn’t necessarily lead to weight gain.
And she adds while we would all like to believe certain foods can get rid of fat, there are no such things as fat-burning foods.
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“Some foods have been found to have the ability to create tiny boosts in metabolic rates like matcha, chili peppers or coffee. However, we are talking really small gains, perhaps you’ll burn an extra 10 or 20 calories.”
But on the flip side, foods high in fat, sugar and low in fibre will make you gain weight. “Meals high in refined carbohydrates trigger a big insulin release, which, when coupled with the high energy density of dietary fats provides plenty of opportunity for the storage of excess energy,” she says.
“These meals are also low in fibre and water, which would fill up our bellies and satisfy us … so we can eat more of them than we could a nice stir fry. That’s why you can’t have just one potato chip, but you’d get pretty full before you overate broccoli.”
Meerman adds he wants readers to understand that 8.4 kilograms out of every 10 kilograms of fat are exhaled as carbon dioxide. He also suggests calorie counting for weight maintenance.
“It is impossible to not lose weight if you eat less carbon atoms than you exhale, and the way to figure out if you’re doing that is to count calories because calories ‘live’ between the carbon and hydrogen atoms in food.”
Nielsen, on the other hand, suggests eliminating all sweetened beverages and minimizing the consumption of refined carbohydrates.
“Instead, focus on adding adequate protein, tons of vegetables and healthy fats at each meal.”
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