Digestion and Weight, Paschimottanasana, 
This beautiful asansa offers many benefits to health and well-being. From a purely physical, structural perspective, its easy to see that this asana stretches the muscles of the lower back and hamstrings offering those who practice regularly greater flexibility in general. However, one of the most important benefits according to the texts of Hatha Yoga like the Siva Samhita is that this asana kindles agni – the power of digestion. In addition, the Siva Samhita states that this asana also brings mastery of vata dosha – the air the disturbs digestion. Hence, this asana reduces vata and kapha doshas. Those who have a pitta imbalance (vikruti) should use some caution as this asana increases heat. This is especially true if a person experience GERD or hyperacidity.
Because this asana helps balance both vata and kapha doshas, it can be used to help manage vata-kapha type weight gain. This is weight gain that has its origin in anxiety eating. Indeed, this asana is very grounding and centering – reducing anxiety. Combined with stabilizing or increasing agni, weight slowly comes off. Naturally, for this purpose, the practice should be combined with a vata-kapha pacifying diet and lifestyle.
Caution should be taken by those who have back problems caused by a disc herniation as this can aggravate the back pain. However, not all low back pain has it’s origin in the disc. Please take care and if there is pain, decrease or eliminate the practice.
Om Shanti.