Thursday, 9 July 2015

BBC Inside Health - Gestational Diabetes, Low Carb Dieting.

A recent edition of BBC Radio 4's "Inside Health" programme covered gestational diabetes and (separately) the experiences of a listener who lost 4 stone (56 lbs, 25 kg) on a low carbohydrate diet.

The programme web site is here, and the mp3 audio file should be available to download via this link however BBC media can be time or location limited so I apologise if it isn't available to you. I do have a copy of the mp3 so get in touch if you need one.

The gestational diabetes (GDM) item was based on the Rosie Hospital in Cambridge where they have recently published work on the sensitivity of different diagnostic criteria for GDM. The article in Diabetologia identifies patients with GDM who fall between the UK's NICE guidance on diagnosis and other criteria and looks at the risks of complications in that group. Full paper here.

Of interest to low carbers was the clear description by a dietitian on air as to how all carbohydrates including starch end up as blood sugar. She went on to say that this meant the hospital encouraged mothers-to-be to change from white bread to wholemeal as the lower GI reduced the blood sugar impact, which was a bit of a let down after a good start. Dr Mark Porter, who presents the program, said on Twitter that the Rosie Hospital's GDM program used diet and carbohydrate restriction, along with exercise, as its primary treatment method. Unfortunately this didn't come over in the audio, perhaps due to editing, so the message was more about changing the colour of your bread rather than eating a lot less of it in the first place.

The second item of interest concerned a listener Mark Robbins who called in to enthusiastically report his weight loss on a low carb diet. Dr Mark discussed this with regular sidekick Dr Margaret McCartney (a GP from Glasgow) and the eminent Professor Susan Jebb OBE. There was a general consensus that low carb dieting does work and that Drs Mark and Margaret see this in their practice patients. It was also agreed that diet trials of up to a year - said to be "short term" - support low carb dieting. Unfortunately nobody much does long term studies, perhaps due to cost or the difficulty of keeping subjects motivated and under control for so long.

Dr Mark asked (at 20m48) if there was a scientific reason / rational explanation of why low carb diets might make weight loss easy and Prof Jebb replied to the effect that "it is just about calories". Perhaps she needs to sit in on Metabolism or Biochemistry 101 classes and remind herself how chronic carbohydrate consumption elevates insulin which impairs the release and oxidation of fat from storage. To lose 25kg of fat in a year requires a fat oxidation rate of 2,9 grams per hour average above the dietary intake (or bodily production) of fat - that's about 25 calories an hour or 600 calories a day and probably 25% of the calorie burn of the listener. Clearly anything that increases fat release and fat oxidation rates is a good thing when you want to achieve this - carbohydrate ingestion does the opposite.

Speaking of Dr Jebb, she appears on the author list of a recent study "Dietary patterns, cardiometabolic risk factors, and the incidence of cardiovascular disease in severe obesity" which looked at 2000 Swedish subjects over 10 years. After much complex maths they concluded "An energy-dense, high-saturated-fat, and low-fiber DP was longitudinally associated with increases in cardiometabolic risk factors in severe obesity but not with CVD incidence" (my emphasis) so once again the "saturated fat is bad" mantra did not stand up to analysis, neither did the "high fibre" approach that Prof Jebb is so keen on. She will never be in favour of low carb diets while she's locked into a high fibre from whole grains and low saturated fat dogma that is increasingly looking "so last century".

Who eats whole grains ? Only pigeons, as far as I can see. Sorry Susan.

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