No additional food production needed, but instead a change to eating lower on the food chain.  The best diet for health and athletics is based on plants.  Below is a good discussion
of the benefits and myths involved:

http://www.nealhendrickson.com/mcdougall/030900puathletesarepeopletoo.htm

And speaking specifically to cycling, carbohydrates are what is needed for endurance.  The differences in fatigue time is astounding - comparing a meaty diet Vs. a complex carb one (this is well references in a great book called "With the Grain" by a female author named Brown.  Unfortunately it is OOP and I'm not sure where the references are, and I'm too lazy to find them :)  Regardless, the link above applies to cycling too.

This came up in another recent thread.  I dropped this link then as well:

http://todd.cleverchimp.com/blog/?p=125

It might be that an electric bike beats some diets, but some diets beat an electric bike.

If the food is available, eating more, and burning more, is a closer match to our pre-agricultural roots:

The average daily energy expenditure, as physical activity, of Stone Age humans is estimated at approximately 5.2 MJ (1240 kcal) and their total caloric intake at approximately 12.1 MJ (2900 kcal) (Cordain et al., 1998). Their subsistence efficiency was thus approximately 2.25 kJ (kcal) acquired for each kilojoule (kilocalorie) expended in physical activity. In contrast, sedentary humans in contemporary affluent societies commonly consume perhaps 8.5 MJ (2030 kcal) with expenditure, as physical activity, of approximately 2.3 MJ (555 kcal) (Cordain et al., 1998), a subsistence efficiency of 3.66 to 1.

PDF article

Well you are really talking about an incremental caloric uptake. But the U.S. diet is typically excessive, calorie-wise, for the age/weight groups. So if anything, you might see a decrease in diabetes, lowering of blood pressure, lowering of colesterol, maybe an increase in joint pain, etc, IMHO. Those rickshaw folks a probably burned out with 12 hour days? This guy (Better Off: Flipping the Switch on Technology) has been doing it with no ill effects. I think currently he is in old town St. Louis.