The SlimFast assorted core powder box contains 10 sachets of SlimFast meal replacement shakes with 4 delicious flavours for you to try.. The Slim Fast assorted core powder box contains 10 sachets of Slim Fast meal replacement shakes with 4 delicious flavours for you to try, This box contains the following flavours: 3x chunky chocolate, 3x Summer strawberry, 2x Simply vanilla, 2x Blissful banana. Each of these delicious shakes contains up to 15g of protein which helps with muscle development and comes in at less than 229 calories per serving. Slim Fast 3. 2.1 plan. Plan and each day eat: 3x Slim Fast snacks or fruit & veg (3x100 kcal), 2x tasty Slim Fast meal bars or shakes, 1x healthy meal (600 kcal or 800 kcal for men). Please remember also to drink at least 2 litres of water and get regular exercise. Substituting two main daily meals with meal replacements contributes to weight loss, and substituting one - contributes to weight maintenance. Key features of Slim Fast assorted core pow