Snacks and a meal are the ultimate sin, so go for snack food that constitutes a real meal. If you're hosting, don't just put out bowls of salty peanuts and fatty crisps: serve vegetables, different types of bread and pieces of meat and fish.
If you make your party food add up to a proper balanced meal instead of just nibbling on everything in sight, you won't pig out as much. And if there are no other options but unhealthy snack foods, make sure you compensate by having a super-healthy meal at your next sitting! Have grilled fish and steamed vegetables with no fat for your next meal. This will give you enough protein, vitamins and fibre to restore your body's balance.