I recently agreed to take part in a study on metabolism at Addenbrooke's. They have data on several patients with thyroid problems or something genetic which affects the metabolism, and they want a bunch of people with no metabolic oddities as a control group. The study involves an overnight stay, which happened last night. This is what I did:
- 4pm arrive, update my hospital records with new address, phone number and next of kin, since they last saw me while I was still living at Arden Road.
- They took my height (168.9cm), weight (c 110kg), blood pressure (136/74) and temperature (a little raised at 37.4)
- Changed into swimming costume and cap for "bod pod" measurement. This involves sitting very still in a pod which weighs you and also sees how much air you displace. It then does some sums and tells you what percentage of you is fat (53.4%, or 58.7kg), and incidentally your lung capacity (which doesn't seem to be on the printout, may have been c 3.5 litres, but I'm not sure).
- The I took out assorted metal jewellery and lay on the dexa scanner, which uses very low level x-rays to determine how you're composed of fat, lean and bone. This came out as a slightly lower total proportion of fat, only 51.2kgs, or 46.4%. And amazingly only just over 2kg of me is made up of bone. Pip was initially concerned that I seemed to have a slightly low bone density for women my age, but apparently it's not anything to worry about. There is approximately 18.5kg of muscle in my legs. I have no idea how this compares to normal :)
- Next I had a heart rate monitor and accelerometer combo attached to my chest, and another accelerometer on a strap round my wrist, and I was free until dinner time.
- Dinner at 6:30 consisted of mushroom pasta (oddly sweet) followed by orange jelly served with a spoonful of black cherry yoghurt on top, and a glass of water.
- At just before 8 we were asked to empty our bladders, and then to collect any more urine passed after that into a bottle for testing later.
- Spent the rest of the evening watching TV and knitting, before retiring to bed with my book after the 10 o'clock news.
- Lights out at 11, and nil by mouth thereafter. Didn't sleep terribly well as it was too warm (I slept under just a sheet!) and the aircon was rather noisy.
- Woken at 6:45 to empty bladder, saving the first 20ml in a separate sample and adding the rest to the main collection bottle. Then doze for 45 minutes.
- 7:30: calorimeter test. The machine measures the air in the room for 5 minutes, then the air you're breathing out (using a hood over your face/chest) for 15 minutes, then the room again for another 5. From the proportion of carbon dioxide they can calculate how much oxygen you're burning. Had to stay still but preferably awake during the process. This is why the stay is overnight, so they can do this first thing and get an idea of your basal metabolic rate.
- A little collection of blood samples were taken next to test for glucose levels, cholesterol and thyroid levels. Apparently they'll only contact me with the results of these if there's anything to worry about. I expect the cholesterol may be a little high, but the others should be fine, as they've been tested OK fairly recently.
- Weighed again in my pyjamas, and then once dressed the pyjamas are weighed too, to find my naked weight.
- Gave back the chest monitor etc, and then breakfast and home.
Whether it's 53.4% or 46.4% my body fat levels still count me as obese, the same as BMI does. Interestingly the latter figure is close to what my scales tell me, and I'd been assuming that under-reads by a fair bit once you get past a certain point, perhaps it doesn't? My blood pressure is fine though (which is nice, since it's often a bit high when taken at the docs), and we'll see if I hear anything back about the bloodwork. And hopefully they'll get back to me and let me know the results of the metabolism stuff at some point too.