help - half marathon on keto

pobalita

Double-posting. I put this in the excercise and fitness forum but looking for all the advice I can get.

I'm looking for some help with fueling for a trail half marathon tomorrow. I've been running halfs for a long time (at least one per month for several years) and generally fuel with about 300 - 400 high carb calories before the run and 1 Clif Shot (25 g carbs) at about the half way point.

I switched to a keto diet just after Christmas to lose some weight and control blood sugar. I have a half marathon tomorrow and I know I am not fully fat adapted. I run three miles or more most days and have no problem, but I bonked severely in an 8-mile trail run (lots of elevation) a few weeks ago.

I don't want to bonk tomorrow, so I'm looking for advice on how to fuel for this race. I don't care if I fall out of keto for a couple days - I just don't want to feel like crap during the race. Should I load carbs tonight? Should I just eat my normal breakfast and Clif Shot? Any advice appreciated.

One final note: I'm not worried about racing or pace. I'm not a competitive runner and only do it for fun so I don't need to fuel like a pro athlete. I just want to finish with a slow, easy pace.

T1DCarnivoreRunner

A non-keto runner would be able to oxidize fat up to about 55%-65% of VO2 max. For me, 55% of VO2 max is a HR of 111. I'm just becoming fat adapted again after a break (in first week), and from BG monitoring (I'm a type 1 diabetic and use a continuous glucose monitor / CGM), that is about right.

So the 2 options are:
1. Keep exertion really slow and just use fat even as a not-yet fat adapted runner.
2. Consume carbs timed to become glucose as they are needed. That means eating about 15 min. before starting and possibly more at about 1 hr.

Marcelynh

I did a full marathon in December and I do Keto. I found that I could eat more carbs during the race (take advantage of those snacks) and stay in ketosis. In fact if I didn't I got too low in blood-sugar and got dizzy. My race had all sorts of stuff out (mini pumpkin pies no less). I'd stay away from gels because they're like pure sugar but I did snack on more carbs than I had eaten in months! lol I didn't go crazy with carbs but my body needed some to keep the blood sugar up. Being too low can be as dangerous as too high in a high exercise situation. The number one thing for me though was electrolytes. I made sure I was up on my electrolytes at all times, especially magnesium because if I get low on it I cramp.

Hope you did great in your half!