Calculating protein requirements

Calculating protein requirements

Adequate protein intake during weight loss is important to help preserve fat-free mass and control appetite1.  Evidence suggests that loss of fat-free mass during weight loss can be attenuated by diets providing protein intakes of ≥0.8g/kg body weight/day1.

Research has been mixed on the amount of protein level required for preventing loss of fat-free mass during severely energy-restricted diets1.  We propose that ≥ 0.8g/kg Adj IBW/day be used as a basis for calculating protein requirements; however, this is at the discretion of the treating healthcare professional.

Consumption of 3 standard OPTIFAST VLCD products per day meets the protein requirements for obesity/weight loss for most females providing between 54.6g and 60g of protein per day, depending upon what combination of OPTIFAST VLCD products are consumed. The below individuals may benefit from extra protein:

  1.  Individuals with a BMI >35kg/m2
  2.  Males
  3.  Individuals that participate in regular physical exercise

There are several ways to provide additional protein to meet increased requirements:

  • Replacing 1, 2 or 3 standard OPTIFAST VLCD products with OPTIFAST VLCD Protein Plus Shakes
  • Supplement with a pure protein, powdered supplement (e.g. BENEPROTEIN)
  • Increasing the number of OPTIFAST VLCD products used 
  • Supplementing with lean protein-rich foods (e.g. meat, chicken, fish and eggs).

The method used to increase protein intake should be based on the best outcome for the individual. OPTIFAST VLCD Protein Plus Shakes can be used in place of the standard OPTIFAST VLCD products at any level of the OPTIFAST VLCD Program. OPTIFAST VLCD Protein Plus Shakes contains 40% more protein than the standard OPTIFAST VLCD Shakes, and also contains less lactose making it a suitable alternative for people with higher protein needs or lactose intolerance.

Research suggests to minimise additional energy and carbohydrate intake and avoid the temptation of food, the addition of a pure protein supplement such as BENEPROTEIN is a useful option. BENEPROTEIN dissolves readily and is relatively tasteless. In addition, BENEPROTEIN is rich in whey protein which may be important for reducing appetite1.

Increasing the number of OPTIFAST VLCD products per day can be another option to increase protein intake. However, if extra OPTIFAST VLCD products are recommended/consumed (i.e. more than the recommended three products per day), carbohydrate and calorie intakes will also increase and therefore may affect ketosis on the Intensive Level.

If using a food source of protein, one serve of protein is equivalent to 65-100g meat, two eggs or 130g fish and can be added to the evening vegetables. This will provide approximately 25g protein and an additional 150kcal (630kJ) to the daily intake of approximately 800kcal.

 Table 5: Protein, energy and carbohydrate content of OPTIFAST VLCD products, plus additional protein sources.

Meeting protein requirements with OPTIFAST products and protein foods


Regular medical monitoring of patients while following the OPTIFAST VLCD Program is important, so that adjustments can be made to the Program or medications.  Read more in our Medical Monitoring section here. 

1.    Gibson, A.A., et al., Do ketogenic diets really suppress appetite? A systematic review and meta-analysis. Obes Rev, 2015. 16(1): p. 64-76.