Losing weight isn't easy for most of us, and neither is keeping it lost – not least because a process called adaptive thermogenesis kicks in, which means our body goes into a power-saving mode because less energy is supplied through food.
In a new study involving mice, researchers think they've found a hormone-signaling pathway that might help. Signaling pathways are like biochemical chain reactions in the body, with particular triggers (such as drugs) leading to effects (such as weight loss).
In this case, the hormone growth differentiation factor 15 (GDF15) stopped mice from automatically lowering their energy use when they ate less, speeding up another metabolic process in their muscles.
"We have discovered that in mice, GDF15 blocks the slowing of metabolism that occurs during dieting by ramping up calcium futile cycling in muscle," says Gregory Steinberg, a medical scientist at McMaster University in Canada.
Previous research has established that GDF15 and its associated receptor GFRAL impact the amount of food mice will eat. Now researchers think it could help keep weight off in the longer term and help with dieting in the first place.
There's still a lot more work to do to analyze the mechanisms in play in this pathway and how they lead to the results shown here. Research also needs to show that GDF15 works the same way in humans, of course – but these early results are promising.
With obesity now thought to be affecting nearly 1 billion people worldwide by 2030 – contributing to other issues such as type 2 diabetes – it's clear that new strategies are needed to get more of the planet's population down to a healthy weight.
"Our study highlights the potential of the hormone GDF15 to not only reduce the desire to eat fatty foods but also simultaneously boost energy burning in muscle," says Steinberg.
Potentially, GDF15 could be used in combination with existing drugs to create appetite-suppressing treatments that are more effective or that are helpful to people that haven't found much success with conventional approaches to dieting.
Scientists still don't fully understand why dieting works for some of us and not for others. There are many contributing factors involved, both in terms of the individual person and the individual diet; an improved knowledge of signaling pathways, like the one outlined here, should help answer some of the outstanding questions.
GDF15 is produced naturally by the body, especially in the liver and kidneys, and we know that its production also surges during pregnancy – the hormone has been linked to morning sickness. Future research will have to investigate potential side effects and the potential benefits of any related treatments.
"Future studies investigating the linkages between GDF15–GFRAL signaling, muscle calcium cycling, and energy expenditure in humans before and after weight loss will be important to further establish the therapeutic potential of this pathway in adaptive thermogenesis," write the researchers in their published paper.
The research has been published in Nature.