Not healthy at all and I am willing to bet a lot of the weight you lost was lean body mass. 40 lbs in a month and a 1/2 is averaging close to 7 lbs per week. 7lbs per month is pushing it if you are trying to do it healthy and keep LBM (depending on where the person is starting from). So I wouldn’t really put much weight to the “advice” is that is what you are trying to give.