Very heavy books have been written about what motivates us, it's seldom simple.
Sexual viability might be one elephant in the room. Most of us agree that certain torso contours signal a healthy mate, but we also agree that acknowledging it is shallow even though broadcasting one's health status dominates the behavior of virtually every animal (sometimes elaborately). So we end up with this perceived conflict: "am I doing this for health or vanity?" yet in nature it's unclear where to draw the line dividing the two.
Lots of: urban hiking, cycling, sprinting
Lots of: fresh meat, seafood, eggs, organs, tubers, starch fruits, vegetables, meat fat, dairy fat, oil fruits
Some: cured meat, dairy protein, sweet fruits, rice, pulses, tree nuts, oil seeds
Minimal: soy, refined proteins, sugar, liquid carbohydrate, grains, refined oils, peanuts