First you should only be weighing 1 time per week at the same time of day and on the same scale. Second use other measurements like body circumference (or how your clothes fit) and/or body composition (body fat testing) in addition or as an alternative to the scale.
If you are weighing more frequently than 1 time per week then you are likely to notice a fluctuation in weight. You may also notice this fluctuation with an active lifestyle. Fluctuations in weight are completely normal. You have not gained 5 pounds tissue (fat or muscle) from a weekend out. However, you are holding on to water weight follow these 5 tips to prevent water weight gain.
2. Sweets and refined starches. Eating a piece of birthday cake at the birthday party did not cause you to gain 3 pounds! However, when you consume more sweets or starches than usual you are more likely to retain water.
3. Alcohol in moderation. Alcohol intake will result in water retention. Try to alternate alcoholic beverages with water.
4. Drink plenty of water. Consistent water intake is very important to preventing water retention. If you are dehydrated your body will hold on to water until you have recovered your hydration. If you did consume more sodium, starches/sweets or alcohol than usual drink more water to rebalance your hydration.
5. Balance your electrolytes. Especially if you live an active lifestyle. When you exercise for longer than 60 minutes or in hot or humid climates you need more than just water. You need your potassium, sodium, calcium and magnesium