毎日大食していると、ブクブク太り過ぎること間違いなし。

、。

If you overeat every day, you'll definitely end up getting fat.

Literal

Every-day binge-eating are-doing [conditional-と], bloatingly gain-too-much-weight [nominalizer-こと] no-doubt.

ブクブク is a 擬態語 (state mimetic) describing something swelling or puffing up — here applied to weight gain, evoking the image of ballooning. ~ていると is the conditional 'if you keep doing X.' 間違いなし is a punchy sentence ender meaning 'no mistake about it, guaranteed.'