? starvation mode

Hi Brooke,
I have been following your model for the past three weeks. I am 50 yo , 5’2 and started at 163 pounds. I have set my target to 121 pounds (would you agree). I have completely cut out flour and sugar and fast from 8 pm to 3 or 4 pm the following day depending on work commitments. In the first week and a half I lost 8 pounds. This gave me a lot of enthusiasm and I have stayed on track. Unfortunately I am now gaining the weight back; 3 pounds. My husband is behind me 100% with trying to loose weight but feels that what I’m doing is putting my body in “starvation mode”. Do you believe the body shuts down to protect from too much weight loss or deprivation?