What it’s like to run a gauntlet of metabolism tests to aid research into a spice-based pill designed to trick the body into burning off excess fat
See more in our gallery: “A human guinea pig in the brown fat lab”
IT’S early evening, and I’m facing a dilemma of some delicacy – whether or not to break wind. Let me explain…
I’m poised to be voluntarily trapped in a room for the night as part of research to find new treatments for obesity at the Wellcome Trust Clinical Research Facility at Addenbrooke’s Hospital in Cambridge, UK. The aim of the experiment is to see if brown fat, a special type of fat tissue that turns energy obtained from food into heat, can be coaxed into burning more unwanted white fat than usual. They intend to do this using a simple food supplement – a daily capsule of spicy ingredients such as chilli pepper or cinnamon – aimed at mimicking the effects of being in the cold.
Recruited as a control, I’ve spent the afternoon undergoing a battery of tests to serve as reference data for how people in reasonably good health burn energy. Investigator Andy Whittle at the University of Cambridge explains that comparisons with this data will help establish whether people burn more energy than normal when kept in the cold (at 18 °C for 2 hours) or when given the spicy food capsules.
I will be confined to a special room for the night, which serves as a human-scale calorimeter. “We’ll treat you as if you’re a fire, measuring how much oxygen you take in and how much carbon dioxide you breathe out,” says Peter Murgatroyd, who designed the calorimeter. In other words, they will be capturing everything that goes in and out of my body.
Hence my dilemma. My fear is that by morning, thanks to forces beyond my control, the room will be embarrassingly uninhabitable. Being British, I’m too shy to ask about this but, eventually, I will inevitably yield to the growing pressure in my tummy and hope no one notices in the morning.
I have earned tonight’s sleep after this afternoon’s flurry of activity, which extracted every last ounce of information about how efficiently I expend energy. Near-naked inside an egg-shaped capsule called the Bodpod, I learned the relative amounts of fat and lean tissue in my body. A dual-energy X-ray absorptiometer informed me that I have 6 per cent less fat than normal for my age, with my bone density spot on. Then I was whisked off to a treadmill to see how efficiently I use oxygen while exercising.
Finally, the calorimeter beckons, where Whittle explains the rationale behind the research before my lock-in for the night. His aim is to subtly turn up the body’s central heating, taking lipid “fuel” from the bloodstream and from white fat cells that store it and send it for incineration in brown fat cells. Experiments in rodents have shown that the colder it is, the more energy they burn off in this way to produce heat. As babies, we also use this system to produce heat. But there is increasing evidence that many adults retain enough active brown fat, or adipose tissue, to do it too.
Whittle reckons this process is controlled by the brain, which orders the extra burning of fat in brown adipose tissue when it gets cold. Recent research has revealed that spicy food – such as cinnamon or capsaicin in chilli peppers – can activate nerve receptors in the skin, gut and mouth, triggering the same brain response as being cold does.
Whittle’s colleague Maarten Soeters cites findings from Japan published this year showing that men with active brown adipose tissue burn more energy than normal when given capsules of capsinoid compounds, similar to capsaicin (American Journal of Clinical Nutrition, DOI: 10.3945/ajcn.111.018606).
Now, Whittle is hoping to see if a mixture of ingredients like capsaicin can trick the brain into thinking it is cold, and coax brown adipose tissue into burning just a little more fat than normal, helping people to lose weight over years. He is keeping the exact ingredients secret for now.
“People get obese through a lifestyle that persists for years, yet we expect weight-loss treatments to work in months,” says Whittle. “The cause has been slow-drip, and your body doesn’t notice the rise in intake and a lack of exercise, so the trick to weight loss might be slow-drip in the other direction.”
I’m proud to have been able to help, but in the morning I can’t resist revisiting last night’s dilemma. Laura Watson, the physiologist who took my measurements, guffaws at my enquiry. “Don’t worry,” she says, “we’re used to it.”