MMA fighter Georges St Pierre was just on the Lex Friedman podcast talking about the effects of calorie restriction on his body composition. He describes the drastic water weight loss because of the drop in glycogen stored in the body. He described carbohydrates having a similar inflammatory effect as salt. I too have dropped my BP to readings of 110/60 while in caloric deficit, but no single reading has much meaning. I may take mine 3-4 times throughout the day and look at the trend over weeks and months.