Maintaining muscle function in to old age

An aside: Public Service announcement. I seem to have a lot of Faceache/book friend requests coming through at the moment. Once upon a time I accepted all friend request and have read some interesting posts as a result. But I don't use Faceache for anything technical. The occasional orchid picture or flat water paddling snap is about it. So now I don't accept friend requests unless I know the person. There's nothing Hyperlipid-ish in my FB posts and the algorisms bury the social stuff I'd like to see if I have too many friends. Sorry if it seems rude, it's not meant to be but there is no way round it. End of Public Service announcement.

Back to the post:

The start of the current gross stupidity of lockdown-2 seems to have vanished in to the haze of the past. I can't remember when I last went bouldering, pre-idiocity. I guess it was some time last December. In the dim and distant past of lockdown-1 the climbing wall was completely reset but during the current period of enforced sarcopaenia only small areas were changed, so I got the chance to see how well I fared on some familiar routes after months of enforced idleness.

Pretty well. Endurance was a bit down and finger strength was laughable but on routes with big chunky handholds going up the main competition wall my bulk muscle seems to cope remarkably well.

On which subject I was interested in this paper put up on Faceache by Jay Wortman

The ketogenic diet preserves skeletal muscle with aging in mice

which is strong in it bias-confirming ability, bearing in mind that the keto mice were not exactly spending hours a day in the gym. It's the same group that produced this study

A ketogenic diet extends longevity and healthspan in adult mice

which is also exactly what you want to hear if you are an old bloke like me with young kids.

But I never blogged about the original paper. It has a certain flaw, common to both papers, which made me slightly cautious. The paper is best described as one of those "think about it" studies. Here are the diets used for both:

and here are the survival curves

The first problem is that there is no mention of gas chromatography. We have no idea of what the PUFA content of the lard was and the lard makes up something over 80% of the calories of the ketogenic diet.

In a deeply ketogenic diet such as F3666 it doesn't matter what the PUFA content is and the lard content is relatively low anyway. But for a rodent diet supplying 10%of calories as protein and maybe 20-25% of calories as PUFA it might matter. It mattered in these papers:

"During this one month [ie the lead-in at 12 months of age] period, food intake was measured to determine the daily food intake required by these animals. At 12 months of age, mice were randomly placed on one of three diets: control, low-carbohydrate diet (LCD), or ketogenic diet (KD). The control diet contained (% of total kcal) 18% protein, 65% carbohydrate, and 17% fat. The LCD contained 20% protein, 10% carbohydrate, and 70% fat. The KD contained 10% protein, <1% carbohydrate, and 89% fat. For the longevity study, food intake was set at 11.9 kcal/day, and decreased to 11.2 kcal/day after weight gain was observed during the first weeks of the study."

The studies combined a ketogenic diet with calorie restriction. Calorie restriction is a known longevity promoter. Duh. And keto didn't maintain a normal weight.

Lard can contain anything from almost no PUFA up to more than 30% PUFA, depending on what the pig was fed on and how adulterated the lard has been with cheap vegetable oils.

So these ketogenic mice had to be on a calorie restricted diet because otherwise they gained weight. They were on a diet containing around 20%-ish of calories from linoleic acid. If they felt a hypo in the middle of the light period they would have eaten to correct the hypo. Pathological insulin sensitivity. Or just the loss of calories in to adipocytes without a hypo would generate simple hunger to off set those calories lost in to fat calls, ie weight gain.

Of course it's just a rodent study and maybe people would be different.

Or, more likely, maybe not.

As a more general point it's also worth noting that the improvement is in the median lifespan, not peak longevity. The first mouse to die was in the keto group, the last in the low carb group. Median does not mean an intervention is invariably perfect for all individuals.

But it's as good as we have at the moment.

Peter