Hi, I am a certified personal trainer. I respect every field specially the more technicals.
However, as far as I know it is not healty to drop more than certain weight per week (please google parameters), in other words is not sustainable because your body has an specific metabolism and some results maybe temporary.
There are a tons of quality foods but you don't have necessary buy all from certain brands or places.
The following is almost applicable to every person: there is a mathematic way to lose or gain weight, not applicable for some medical conditions or deficiency of minerals.
Just calculate your daily calorie requirements (basal), There are a few calculators on internet that can help.
For example if the result is 2,000 calories daily just consume 200-500 less calories than you need. That would approx 1,500 per day. You will start to lose weight in a healthy way, just eat balance (protein, carbs and lipids) and you will be fine.
Do not do that for a long time cause your body needs the fuel (food) to work well. Just rest eventually from the hypocaloric (deficit of calories) diet.
