Yoga is suitable for all people, it doesn’t matter what nationality, race or culture they are. Yoga does not divide people based on racial, ethnic, cultural or religious principles. That’s why yoga is equally well suited for both people of the East, and for the people of the West. Each and everyone can learn something useful from yoga practice. No advance skills such as, for example, flexibility, are needed. If a person as doctor say "is practically healthy", he/she can practice yoga. If there is any doubt about health, you should always consult with the doctor.

Yoga doesn’t forbid having sex. Generally yoga is not a system of prohibitions and permissions. Yoga - a system of self-exploration, in which recommendations are given based on experience, which was obtained by yogis and yoginis in the past. None of yogins would impose a way of life on others, prohibiting or allowing something. So you can have sex as usually, as you normally do. In yoga there is no list of what is allowed and what is forbidden in sex. In other words, yoga doesn’t get into your bed. But the only thing yoga insists on is observing of the first and second principle of yoga. That is, the first principle of yoga says that nobody should suffer from your manifestation of sexuality. And the second principle tells you not to fritter away, it invites to spend your sexual potential reasonably, for giving delight to your loved ones and accordingly to yourself as well as for the continuation of life (having children), for the spiritual practice of self-exploration.
Sexual energy is one of the highest and greatest ways of our manifestation. Sex gives pleasure, and a huge potential, which leads to the birth of a new universe, a new man. Thereby proper use of this potential can provide a solid base for self-exploration and spiritual growth. There are special areas in yoga, that teach treating of the sexual energy. In these areas it is said that sexual energy has two components, and due to our inexperience we tend to see them as one. The one part is the energy of pleasure, the second part is the energy for the continuation of life (having children). Yoga recommends being aware of this difference.
During sex yoga invites to learn using the part of pleasure for both of partners, if you do not plan on having a baby after sex, and try as much as possible not to spend the other part often as it is intended for the continuation of life. Saving of this second part sometimes is called as chastity or brahmacharya. There is no question about having sex or not. Everyone decides this for himself/herself. The question is how to have sex without loss in the part of potential, intended for continuation of life.
Unfortunately, yoga is disappearing, and only few people know the depth of this teaching. Due to this reason, the myth appeared that yoga is against sex - this is an example of penetration of the partial knowledge to the West, creating great confusion in the minds of the ordinary people.
Sections of yoga, which study these questions, sometimes are called Tantra Yoga, Yoga of Sexual Union, and Yoga of Amorousness. But, if you have not learned them yet, you can have sex as much as you have always done, trusting your experience, feelings, and senses.
Sometimes, if you want to achieve a particular breakthrough in some yoga practices, it’s recommended not to have sex, but to accumulate a certain life potential, which would facilitate rapid results. This could be extremely useful and effective, especially if you do not have sexual partners for practicing of yoga.

There is only one criteria of success in yoga - a habit to practice yoga. If you have it, then you have succeeded in yoga, and all useful results will come with time. If you don’t have the habit of doing yoga you could eventually lose the flexibility and slimness and everything else.

Disease must be treated by medicine practitioners. Yoga does not substitute the medicine. Yoga is a system of self-exploration, which helps to maintain the health on a good level and sometimes deals with some diseases, but it is rather a side-effect of self- exploration. If you have any diseases first of all it is necessary to seek qualified medical advice. Of course, there are cases where yoga helps to overcome the disease, which could not cure by medicine, but it’s difficult to say for sure that this will be your case.