I ve gained weight since I started drinking Spirulina (skim) milkshakes (397 cal) substituting meals. How can this be?

When you first start a diet, and decrease your calorie intake significantly, your body may react in different ways. How many shakes are you having pre day? Many people do "juice" diets, where they blend fruits and veggies and only drink those, but I' ve never heard of the milk shake diet. Sometimes when you cut out complex carbs and fats your body reacts by storing fat, because it thinks you're starving. It grabs all the extra weight it can, in preparation for not having food later. It's a survival technique hardwired into our genetics. You have to keep up with any diet and ALSO add fitness into your life style to see any results. Temporarily gaining a couple pounds at the start of a diet can happen.

Wow, I did not know that. I'm going gun-ho on this but I feel somewhat ill. I make 1 shake in the morning (I cup milk) and stretch it during the day. It's my third day in less than 1800 Cal/day and I feel bloated during the day but hungry at night. I have to incorporate fitness yet. I'll do so tonight. Even if it's some push-ups. Thanks!