I can attest that this so true. Many years ago, I attended a one day camp by Swami Ramdev. First thing he did was asked 10 people with over weight and 10 people with high BP to come to the stage and weigh themselves and have their BP measured with doctors recording everyone's weight.
We had no clue what he was doing, but after that he did one and half hour of deep breathing and Kapalbhati (fast breathing technique). Beyond everyone's belief, every single person on the stage with over weight had lost one lb, but a few lost more, one women lost seven lbs. Also every single person who had high BP had lowers their BP, some by ten points.