How can we maintain a diet on a vacation?

You can have a healthy diet everywhere, whether on holiday or not, by following some of those simple tips:

• Have whatever food available but control your portion size. 
• Don't wait until you're hungry, have small meals throughout the day i.e5 small meals.
• Drink plenty of water throughout the day.
• Start your lunch and dinner with a salad. This will help you feel full and end up with a smaller portion of the main meal. 
• If you have the option, try to opt for food options that are high in protein (chicken, meat, fish, pulses) and complex carbs (whole grains, brown bread) and low in simple carbs (white bread, white pasta, pastries) and fat. Otherwise, as said earlier just control your portion size.  
• I know resisting the dessert while on holiday can be a little hard but if you must have one then try to share one dessert with another family member, or choose a fruit salad instead, or maybe even have one and skip it the other day etc. 

I hope you find some of those tips helpful. 

• Restaurants often serve large portions, and we tend to eat more when more food is in front of us.
• Restaurant menu items are often high in calories, fat, saturated fat, cholesterol, and sodium and low in fiber.
• At restaurants, you usually have no idea how many calories or grams of saturated fat are in the dishes you order.

Maintain a what ?!! :) Did you mean hair dye?