I've went low carb (old Atkins Phase 1) several years back with fair to good results but even after going to Phase 2 didn't sustain it and fell off the wagon. My cycling kept the weight off but I had come to believe that somehow the carbs were needed for my cycling performance. Well, the combination of a long bad winter, some health issues, and some family and work demands (along with me being lazy and indulgent) put 15 pounds back on my carcass and it wasn't coming off. Still I was downing granola bars, cookies, sports drinks, and the like justifying it as I "need" the carbs to ride well.

Today marks one week that I have been back on a low carb diet somewhere in the neighborhood between new Atkins Phase 2 and South Beach. I'm seven pounds down (yeah, I know, water weight and newbie losses) and today was my first real test on the bike as I have been working 24-hour on-call for the past five days and couldn't do much more than tool around the neighborhood.

The old: 500+ kCal high-carb breakfast and 200-300 kCal primarily carbs every hour = 1,600 - 2,100 kCal which was mostly carbs on an 80-mile ride. Average speed of my long rides (50-100 mile) so far this summer 15.4 mph.

With almost no carbs I expected this to be a slow, rather short ride despite the beautiful day.

Today: 200 kCal breakfast of protein and fats (2g carbs) and a total of 450 kCal of low carb snacks during the 80-mile ride. Average speed 15.3 mph and that considers that I did the opposite of what I usually do and started out with the wind during the first half of my ride which is mostly uphill on a slight grade with a few rollers and one short 8% grade climb to the mid-point of the ride. The second half of the ride was rollers with a net downgrade for about 5 miles then almost dead flat into a 4-8 mph wind quartering or directly from the front.

I felt just fine, never hungry, never bonky. Only during the last 16 miles did my legs start complaining and I started to have trouble maintaining an even speed. After the ride, no severe hunger, no shakes, no cramps. I put my stuff away and had a 300 +/- kCal low-carb lunch and feel just fine. Total calories so far today = 950-1,000 with approx 12g carbs compared to 2,000-2,500 and a crap load of carbs the way I had been eating on similar rides.

Low carb guys, you may have another convert

Not to get into the low-carb diet thing, but you really only need carbs when you need carbs. If you calculate the calories required for a 50 mile ride, it doesn't require much, if any, carb loading, but after the first 30 miles or so you would benefit from some minimal carbohydrate intake. The carbohydrates required before a very long ride, and during long rides, should not be confused with what works well for your overall diet and weight control (you didn't gain the 15 lbs while riding your bike). Tooling around the neighborhood requires little more than light protein replacement for an all out effort, and a glass of water for lesser efforts.

Carb/fat ratio for cycling depends on two things:
1) What you want to do.
2) What you want to tune your body to do.
There's a difference.

I'll tell you a little about a flat 202 mile ride I just did. I know about how many calories I went through, because I carry with me almost everything I eat on a ride of this length. Breakfast was ~400 cal. During the ride I tried to eat (drink, actually) about 2250 calories. I had a little left over at the end, so maybe 2000. At food stops, I grabbed ~500 cal. of this and that. Elapsed time on the ride was ~15.5 hrs., of which ~12.3 were spent pedaling. It was quite hot, so I spent a good bit of time off the bike, hydrating. So that's an moving average of ~16.4. I figure calories/hr. using elapsed time, because max intake is governed by stomach emptying time, not by pedaling time. So that was ~160 cal./hr, which was about right for that pace, as I was strong all the way to the finish. Of that, 85% or ~530g were carbs, and ~94g were protein. I eat almost no fat on a ride of that length.

I'm 69 and of below average genetics for a cyclist. I train, though. I did this ride on a tandem with my wife. 10 years ago on a single, I did this same ride in ~10 hrs. pedaling time, and under 12 hrs. elapsed, so a moving average of 19.9 for ~200 miles. That ride, I went through about the same number of calories, but in much less time, so ~210 cal./hr. I was younger, and putting out a lot more watts.

10 years ago I did my last RAMROD, 154 miles and 10,000', with a best time of ~9.5 hrs. elapsed time, or ~16 mph counting stops. Near the end, I covered 25 miles of slightly downward trending but upwind road in exactly 1 hr., so my fueling was good. For that ride, I fueled at ~250 cal./hr, as much as my stomach could take, with that same carb/protein ratio.

My weight has been about the same for the past 15 years, running about 5 lbs. over what it was when I was mountaineering in my early 20s. On a recent tour, I happened to have the opportunity to take my BP: 106/54. My doc says my lipids are "perfect."

I understand that not everyone wants to do these sorts of rides, but these sorts of rides are what the usual recommendations for macros are modeled upon. Nothing in the above is in the slightest unusual, other than I am a little older than most folks and tune my nutrition better than most folks. I hope you don't take it that I'm bragging: I'm not. There were and are many people much, much faster than I am. I was always at the back of the pack on every climb. Now I'm off the back, but I keep on keeping on.

I'm just saying, this is what almost any rider can do, and most can do much better. It does take a little knowledge of nutrition and a lot of training.

For an 80 mile group ride, 10 years ago I would go through about 1000 calories and have ~18 mph average with 4000' of climbing. If you think about what I've been saying and do a little calculating, you'll see that, though I figure by the hour, I actually eat by the mile, not so much by the hour, at a rate of ~12.5 cal./mile for rides of up to 200 miles, slightly more for rides with a lot of climbing.

There's already a thread for this. Perhaps you'd like to check in there:
https://www.bikeforums.net/training-n...heck-here.html

Mods, please move this thread if appropriate