I'm a prediabetic, and I'm trying to keep off meds, so I'm on a very low carb diet. Maybe not keto, i.e., <20 carbs/day, but certainly less than 40 grams per day. 100% of my carbs come from vegetables, with a couple of cups of blueberries thrown in about twice a week.

I've lost 42 pounds since last August. My LDL has dropped by 50%, from 176 to 84. My HDL has stayed about the same, at 51. Triglycerides are 48, which is pretty low. In other words, LCHF hasn't hurt my lipid profile one bit.

Resting pulse has dropped from 60 to 51.

I've actually felt more energy, perhaps as a result of losing so much weight. I ride 3 times a week, usually for around 40 to 45 miles on the weekdays and 50+ miles on the weekends. I use a Fitbit, and the results on my most recent ride were as follows: 132 minutes in peak zone (152 bpm +), 59 min. in cardio zone (135 - 151 bpm), 12 min. in fat burn (110 - 134 bpm). This ride was a bit more intense than typical rides, but not that much.

I notice that around 3 1/4 hours into every ride, I start having problems with lactic acid buildup, especially if there's been more than 2,000 feet of climbing.

I don't eat any carbs during my rides. I use Hammer Endurolytes to replenish my electrolytes during the ride, about 1 tablet per hour mixed with a bottle of water. If I really need a snack in the middle of a ride, I eat nuts.

I don't view LCHF as a "fad diet" -- it's what has kept me off of diabetic meds and what is keeping me from losing my feet and eyes.

But it has also not hurt my riding. Yes, I couldn't be a racer (but at age 67 I couldn't do that anyway), but it's overall been a great help to my overall fitness and my bike rides in particular.