Possible Clues:

• What pasta and potatoes have a lot of
• Rice and potatoes, e.g
• Bread nutrients, informally
• Keto diet restrictions
• Energy sources, of a sort
• Pasta and spuds, to marathoners
• Pasta, potatoes, etc
• Marathoner's prerace intake
• Seats, say, with black padding — stuff those in to fill out?
• Atkins dieters' no-nos