JugglerDave

I'm a relative newbie... over the past year I've lost about 18 pounds, and I do a 32 mile ride about once a week.

I was wondering what the maximum calorie deficit can be for a single ride? I've read that you have only 1500-2000 calories of glycose in the muscles to be used before bonking. I've seen posts recommending eating 250-350 calories per hour. I would estimate that for a fairly fast riding pace 600 calories per hour is not out of the question, and 35-40 calories per mile is about right for my weight (175) and speed (16 mph on a hybrid).

My question is whether the 1500-2000 calories of glucose is an upper bound on the net calorie deficit during a ride, because it's very difficult to replace the glucose stores while riding?

E.g. assuming all the above, does this mean that I can either ride for 40 miles without eating anything, to the point of bonking, and burn about 1600 calories? Or I can burn 600 and eat 300 calories for net -300 calories, for about 5+ hours (75-90 miles) and have the same 1600 calorie deficit maximum?

-=$>Dave<$=-

terrymorse 

Calorie deficit calculation is useful in determining how much recovery fuel you need. Depending on the intensity level of your effort, you can ride for hours without eating anything and not run the chance of bonking. Once you start exercising beyond about 72% of your max. heart rate, you start dipping into your glycogen stores, and taking in carbs during the ride is important to prevent the bonk.

An example: Today I did a 4.5 hour ride, burned about 3000 kcal, and took in about 900, for a deficit of 2100 kcal. It was a "tempo" ride, so I was drawing down my glycogen at a moderate rate. Once I finished the ride, I drank a recovery drink and have been snacking on carbs every hour.

Guest

Well, do you really want to know how to eat optimally for fat loss from riding, or do you just want an estimation that may or may not work, which could lead to even more frustration down the line when things possibly don't work out?

Ok, it's a long, run on sentence, but it's so difficult to know how many calories you are burning without some type of measurement. You are asking a REALLY great question- and the best way to answer it is to find a dietitian or nutritionist that has the BodyGem- the basic ones measure resting metabolic rate so you can figure out how many calories you burn throughout the day, but the more advanced BodyGem devices will measure you while you're exercising, and it can tell you how man calories you are burning while you're working out. Based on those measurements, the nutritionist or dietian can sit down with you and give you an optimal eating plan based on the goals you want to work towards.

Dood, I don't know much about you, so it's hard to say. Folks with a higher amount of muscle, or more testosterone, or more active thyroids, or more physically active throughout the day will burn more calories. On the other hand, if someone is very active but not eating very much, then they actually could be burning less calories, since the body will work to conserve energy, since you're not fuelling it correctly. Hence my thought that it would be cool for you to see a dietitan or nutritionist who offers an eating plan based on using the BodyGem.

Koffee

JamesV

Calorie deficit and bonking are not related at all. Calorie deficit is useful for weight loss management. Bonk management is useful for maintaining performance on the bike.

There is no upper limit to calorie deficit. If you bonk, and continue riding, your calorie deficit continues to go up. Except when you completely run out of body fat. Then you die.

Bonking just means that you've burned all your muscle and liver glycogen stores and your body is switching to the less efficient 100% fat-burn metabolism. You have to slow down drastically when you bonk because the energy release rate is slower on fat only. You want to avoid bonking because you don't want to lose performance and because you don't want to feel bad (hard bonking is not pleasant, i've been there).

You're right, you generally cannot replace glycogen on the bike. The purpose of Gu, sports drinks, etc. is to swamp your bloodsteam with carbs so you burn that and preserve your liver and muscle glycogen. All-out efforts like sprints and hard climbs really burn the glycogen. That's why most riders typically only have 1 or 2 attacks in them.

You worry about calorie deficit for the whole day, not for the ride. To lose weight the generally accepted target is a calorie deficit of 500 cals per day. At the same time, you can manage food and drink on long rides to avoid a bonk as well.

example

breakfast 500 cals
ride -1200 cals
sports drink on ride 300 cals
lunch 500 cals
dinner 1200 cals
base metabolism -1800 cals

Total calories for day = -500
During ride -1200 + 300 = -900, less than -1500 bonk limit, so no bonk

JugglerDave

Thanks for the replies. I guess to summarize it seems like I can have "unlimited" calorie deficit as long as my glycogen stores don't deplete. And glycogen depletes at various rates depending on level of exertion. And it's difficult to replace glycogen on a ride.

So, I can ride moderately ("tempo") for a long period of time, and burn more calories overall than if I ride aggressively w/ hill attacks, etc. for a short period of time because my glycogen will deplete quicker.

Sound right?

-=$>Dave<$=-

JamesV

No, not quite. Let's say you ate a 500 cal breakfast plus you have 1800 cal of glycogen stores. You have 2300 cal to burn before bonk whether you do it in 3 hours of tempo or 1.5 hours of intervals and climbs. Either way your calorie deficit is the same: 2300 cal minus lunch and dinner.

... but that's just an approximation. I saw a study somewhere that suggested that if two cyclists did the same amount of work (same total watts) but one did it easy and the other hard, the hard worker actually spent more calories than the easier one did. Has to do with more heat generation, faster heartrates, faster metabolism, etc.

My personal experience with weight loss is that I seemed to get the best results from including aggressive riding. IMHO to get the most out of your 32-mile ride throw in some hard, aggressive climbs or intervals. Go easy on the sports drinks. On non-riding days off try to keep the calorie intake close to your base metabolism (guessing 2000 calories).

Good luck with your goals!