If you keep staying up late every night, you're going to ruin your health.
Literal
Every-night late-night-doing is-[conditional-と], body [object-を] break [informative-よ].
夜更かし ('staying up late at night') is a noun form — 夜 ('night') + 更かし (stem of 更かす 'to pass through'). 体を壊す ('to break one's body') is the idiomatic 'to ruin one's health.' ~ていると ('when/if you keep doing X') pairs the habitual ~ている with the temporal/conditional と — the consequence follows naturally from the habit.