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Your New Year Weight Loss Resolution: Nuclear Data Reveals Exercise-Weight Relationship


Using doubly labelled water, a study has confirmed that your body attempts to counter the calories you burn in extra exercise activities, and that losing weight through exercise alone is even harder for overweight people. (Photo: Adobe Stock)

It’s that the time of the year when many people across the world overindulge in seasonal and festive delicacies and commit themselves to setting their bodies right in the New Year. At the heart of resolutions is a fresh gym membership and an intensive exercise regime that promises to deliver results in a short time. Despite best efforts, however, this approach doesn’t work for everyone — why is that? Why is intensive exercise not the most efficient way for some people to lose weight?

A study this year, using data from the IAEA’s Doubly Labelled Water Database, reveals insights on the effectiveness of exercise in spurring weight loss. The results aren’t as straightforward as you may think.

“When enrolled into exercise programmes for weight loss, most people lose a little weight, some individuals lose lots, but a few unlucky individuals actually gain weight,” John Speakman, professor at Shenzhen Institute of Advanced Technology and University of Aberdeen told the MailOnline. He’s the chair of the IAEA's Doubly Labelled Water Database Management Group and one of the authors of a study confirming what many of those seeking to lose weight have long suspected, that the calories shown burned on a treadmill’s display does not reflect the reality of the calories burned in your body. 

According to the study published in Current Biology, in individuals with a normal body mass index (between 18.5 and 24.9) the body will offset the calories burned performing exercise by 28 per cent — meaning just 72 per cent of the calories will be lost over the course of the day. With age and weight, however, this ratio gets even worse, and those with the highest body mass index will only lose 51 per cent of the calories burned in exercise. The study confirms that individuals differ in the way their bodies budget energy use, and people living with obesity may have difficulty losing weight as their bodies are efficient at hanging onto their fat storage.

“There are many health benefits that can be gained by being more active and exercising, but relying on exercise alone will not help you lose weight,” said Alexia Alford, an IAEA nutrition specialist and co-author. Guidelines for weight loss do not take into account the reduction of calories burned in other life functions as the body compensates for the calories burned during exercise.

“If you increase your activity your body will compensate for it in other areas and cut back in the calories burned in breathing, digesting, fidgeting, and in general body maintenance and function. This can actually add up to quite a lot,” she explained. Alford advises to not rely on exercise alone to lose weight, but to pursue a more balanced lifestyle in all aspects and that diet is key to maintaining a calorific deficit for weight loss. Her guidance, and the conclusions of the study, come from data obtained through a nuclear technique involving doubly labelled water (DLW) and were made possible thanks to an IAEA database.

There are many health benefits that can be gained by being more active and exercising, but relying on exercise alone will not help you lose weight.
Alexia Alford, IAEA Nutrition Specialist

Answers in a DLW database

DLW is the name given to water rich with a known amount of two stable (i.e. non-radioactive and harmless) isotopes: deuterium and oxygen-18. By measuring a study subject’s urine over a period of 7 to 14 days after drinking DLW, researchers can very accurately calculate a person’s total energy expenditure. The technique is superior to others in that it allows study subjects to continue to live their normal lives and accounts for calories burned both in activities and generally by the body’s metabolism.

Using DLW for studying a body’s total energy expenditure isn’t new, but the high cost of oxygen-18 and the machines to measure it, has meant studies have been small scale. In 2018, the IAEA was approached by a group of DLW investigators that wanted to make their datasets more widely available, and the IAEA DLW Database was developed. Today, the database has DLW data from over 7,600 people making it by far the world’s largest collection of such data.

Free and accessible to researchers with clear and defined research questions approved by the management group, the IAEA DLW Database has a diverse spread of data that includes athletes and high altitude runners, cancer patients and people with cerebral palsy. Most of the data comes from studies conducted in Western countries, such as the United States and the Netherlands, so the IAEA is looking to expand the data set even further with data from Asia, Africa, and Latin America, and in 2022 will start a coordinated research project that will add more lower-income country data.

“Our database is an invaluable asset towards better understanding how the human body functions. This exercise study is a great example; whereas most DLW studies generally involve about 30 subjects, the exercise study had over 1,600, making the data very robust,” said Alford. “The data in the IAEA DLW database is an untapped treasure trove, and we encourage researchers to reach out to us to gain access to its contents, and contribute their own datasets.”

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