While diet is typically the most important factor in weight gain, other important factors include
You Are Not Sleeping Enough
The human body transforms during sleep, and not getting enough sleep can lead to weight gain, among other negative consequences.
You Are Overeating
Snacking frequently, cheat days, and high-calorie meals all promote excessive calorie intake.
Muscle Gain
If you've been eating well and lifting weights, you're probably gaining muscle, and weight gain is a healthy weight gain.
You're Weighing Yourself Wrong
It is best to weigh yourself first thing in the morning; weighing yourself after eating will result in weight gain.
Skipping Meals
Skipping meals frequently leads to overeating and binge eating, which is the primary cause of your weight gain.
Pro-tip
Physical activity combined with a calorie-deficit diet plan is one of the most effective ways to lose weight.