They hunted, killed, feasted on their prey, and then FASTED!!
See, humans were designed to be able to go long periods of time without eating. Our bodies are so efficient that we can go up to 40 hours without eating before we truly begin to break down our own muscle.
Unfortunately, in today's culture we've trained ourselves to crave food every few hours from the moment we wake up to the moment we fall asleep and physiologically that is not the way we were built.
Men and Women were practicing Intermittent Fasting without realizing it, explaining why their bodies were lean, fit, and more muscular in order to survive.