1. Low Fiber diet. Aim for 25-35 grams of fiber a day. The best way to incorporate these are through legumes and lentils like beans. Also your veggies and complex carbs. 1 cup of beans typically yields 12-18 grams of fiber alone!
2. Not enough water in our diets. Aim for a gallon a day. Which is 128oz or 8 (16oz) water bottles. Minimum we should get 64oz, so 4 water bottles a day. The best tip I can give you is start early. After waking up aim to get 32oz of water before you get to work. Then the rest of the day simplifies.