Opinions on what constitutes a good/perfect diet abound, not the least in the yoga world.
One diet that’s had a lot of press is the severely restricted calorie diet; it’s meant to promote long life, although it may limit your opportunities to socialise.
The low carb diet is popular around here because those pesky carbohydrates are reputed to stack weight on your body. But the diet can be protein heavy, with lots of dairy, meat and eggs.
A colleague of mine who has considerable sway with his yoga students advocates a raw food diet, mainly vegetables and fruit, foreswearing any processed foods. Maybe it’s my eastern European heritage, but I like cooked foods, especially in cold weather.
I used to stay away from eating starches because I thought they would make me fat, but I’ve gotten over that fear. As I’ve aged, I’ve become more moderate in the amount of food I eat and more careful to balance my diet. I just don’t feel good if my regime is unhealthy – that is, overeating or bingeing on junk food. But I also am not super strict: being relaxed is a good digestive.
It is true that if you do yoga practice long enough and regularly, you gradually arrive at a diet that will be good for your body/mind. Diet will then be a complement to yoga practice and help your development on all levels: physical, emotional, mental and spiritual.
When your diet is optimal, Samana (Sutra III-41), one of the 5 pranas, contributes to stoking the gastric fire, aids digestion, and maintains functioning of the abdominal organs. It also controls the heart function and through it our very life force.

Samanajaya jvalanam

By the conquest of samana vayu, the yogi gains control over the element of fire (tejastattva).*
*Light on the Yoga Sutras of Patanjali, B.K.S. Iyengar.