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The common practice for calories and protein requirements calculation in obese patients is using actual weight for calories and Ideal body weight for protein.
This practice is followed by ASPEN
The recommendation for calories and protein for stable adult obese patients:
Calories Amino Acids Fat
Grade I obesity 15-20 Kcal/Kg (ABW)/day 2 gm/kg (IBW)/day 0.3-0.5 gm/kg (IBW)/day
Grade II Obesity 10-15 kcal/kg (ABW)/day 2 gm/kg(IBW)/day No need for the first week, start with small dose 0.3-0.5 gm/kg (IBW)/day if patient is still NPO in order to prevent EFAD
Grade III Obesity 10-15Kcal/Kg (ABW)/day >2 gm up to 2.5 gm/kg/day NO need for the first week, start with small dose 0.3-0.5 gm/kg (IBW)/day to prevent EFAD
Some clinicians use Adjusted body weight for calories requirements. If so, you may add up to 20% additional to the above numbers for calories.
Also, close attention must be paid to other micronutrient deficiencies like vitamins and trace elements. They may need mega doses and off course to monitor those levels and adjust accordingly like fat soluble vitamins, vitamin B1 and B12, selenium, zinc, and copper.
For calories, you have the other option of using IBW and the range will be 20-22 kcal/kg. I tried both ways ( IBW and ABW) and all will end by the same numbers.
There are different schools: we use Adjusted Body Weight (AjBW) for any patient who is 20% above IBW. (some references state 30%)
Estimate Ideal body weight in (kg)
Males: IBW = 50 kg + 2.3 kg for each inch over 5 feet.
Females: IBW = 45.5 kg + 2.3 kg for each inch over 5 feet.
AjBW = IBW + 0.4( ABW* – IBW)
*ABW is Actual Body Weight