Dropping Weight, Not Performance

Q: Hey Gale - I'd love to get your take on something. I've been researching this next topic for my cycling group: encouraging riders to determine whether or not they're eating enough when training. (Who better to write this than Mr. Bonk himself?)

When I did some analysis on my own caloric intake and taking into account the variables of (1) Body weight, (2) Riding intensity, and (3) Duration, I quickly realized I was consistently training at a caloric deficit. Ok, so the simple answer could be: eat more, right?

Now here's where it gets tricky. If you have a rider who wants to deliberately subject themselves to burning more calories than they take in for the sake of weight loss (and I must confess I have a few pounds I'd like to shed), the $10,000 question is, at what point does your caloric deficit begin to affect performance on the bike? I found the following statement and I think it is pretty revealing:
"If you ride at too hard of an intensity you'll be depleting the glycogen stores within your muscles rather than training your body to burn off fat."
So, given the above statement, how would a rider know when they've taken the advantage of calorie-burning from exercise to the point of glycogen-depletion from muscle tissue, which presumably would be the threshold at which a rider would begin to experience fatigue and a negative affect on performance?
When I read the literature on manageable and safe weight loss, there seems to be a consistent figure of 1.5 to two pounds per week that is considered safe and reasonable for weight loss. Heck, I've lost that amount on one ride from becoming both dehydrated and malnourished! Yes, Mr. Bonk may not be a good example, but in our cycling world there are many riders looking to find that balance between maintaining fitness and reducing weight.
Can you help? Thanks - G.A.

A. Mr. Bonk, you have several good questions. Let me try to hit each one:

?How many calories per day can you cut without cutting performance?

I've never seen any specific research on this, but my personal experience and experience with other athletes yields an answer of 200 to 500 calories per day, average.

I write "average" because if you do a big ride on a weekend day, you might find yourself at an 800 to 1,000 calorie deficit at the end of that day. If you keep trying to maintain an 800 calorie per day deficit over the long haul, performance will suffer. People that have no sport performance expectations can run that low, but competitive athletes cannot.

The day of the big ride, you might end up being low by 800 to 1,000 calories, but the next couple of days will likely find you eating a little more. There is nothing wrong with that, as long as you keep the weekly deficit at an average of 200 to 500 calories per day. Bigger people can usually go to the higher end and smaller people on the lower end.

If you need formulas to estimate caloric needs, see the column Maintaining Your Lean Mean Racing Machine.

?"If you ride at too hard of an intensity, you'll be depleting the glycogen stores within your muscles rather than training your body to burn off fat."

It's not exactly black and white. A point of clarification is that we are producing energy aerobically (primarily burning fat) and anaerobically (primarily burning glycogen) all the time, in concert. Even as you sit relaxed in your chair, reading this column, you are producing some energy anaerobically.

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