There are so many ways to eat beans and lentils and there are a large variety. How are you eating them?
You might want to try different ways such as hummus, roasted chickpeas, split pea soup, lentil soup, black bean burgers, etc.
Also, all plant foods contain a mix of the two types of fiber so you can certainly fill up on vegetables for a low calorie fiber boost but I personally eat beans daily so I'm a fan.
You can't out-exercise poor eating habits.