E-Journal Club – October 2022
Greetings,
We are finally getting back to a more regular journal club schedule here at UVA, and we hope to make our critical evaluation of new research a regular feature of our website again. Carol Parrish is retiring from her position at UVA at the end of October 2022 and we have been working to reorganize our staffing to maintain our level of clinical excellence.
We have pulled an older article “from the archives” for our journal club, because recent social media posts have referenced this study as data in support of avoiding hypocaloric feeding for obese, critically ill patients.
October Citation:
Jeevanandam M, Young DH, Schiller WR. Obesity and the metabolic response to severe multiple trauma in man. J Clin Invest. 1991;87(1): 262– 269.
Summary:
This study was completed on what appeared to be a convenience sample of 17 adult trauma patients (7 female, 10 male). The 7 obese patients had a mean BMI 36.2 kg/m2 and the 10 non-obese patients had a mean BMI 25.0 kg/m2). Injury severity scores were similar between the 2 groups of patients (27 vs 28). After the patients were resuscitated and stable (48-96 hours after admission), indirect calorimetry measurements were completed, glycerol turnover rate was calculated to determine whole-body lipolysis rate and [15N]glycine was used to determine whole body protein turnover.
No subject was allowed any nutrient during the study. The researchers did not measure actual lean body mass nor total body fat of the study subjects. Instead, they assumed that all of the obese trauma patients (mean age 46.1 years) had 43.4% of their weight as fat, and the non-obese patients (mean age 38.2 years) had 16.5% of their weight as fat, based on the results of different study, where the subjects were all male and had a mean age of 24 years (1,2).
Inclusion and Exclusion Criteria:
Inclusion criteria:
Adult trauma patients requiring ventilator support
Exclusion criteria:
Sepsis, multiple organ failure, diabetes, recent weight loss, hepatic, renal or malignant illness.
Major Results:
The protein turnover rates were not statistically different between the obese and non-obese patients when expressed as absolute values or when normalized to body weight. However, the obese patients had significantly (p=0.01) greater protein turnover (5.76 gm/kg LBM) than the non-obese patients (4.11 gm/kg LBM) when protein turnover was expressed as a function of the estimated lean body mass (LBM). Protein synthesis rates were numerically, but not significantly, greater in the obese patients.
The total daily urinary nitrogen loss was significantly (p=0.025) greater in obese patients (22 gm N/day) compared to non-obese patients (14 gm N/day), but was not significantly different between the groups when expressed as a function of body weight. Muscle degradation rates (g/day) and 3-Methyl histidine excretion (umol/day) were both significantly (p=0.025) greater in the obese compared to the non-obese patients.
Net fat oxidation (kcal/day) expressed as an absolute value or per Kg of LBM, was significantly less in the obese patients. Whole body lipolysis (kcals/day) rate was numerically, but not significantly less in obese patients than non-obese patients as an absolute value or expressed per Kg LBM, but was significantly less when expressed per Kg of estimated total body fat. Net protein oxidation (kcals/day) as an absolute value or per Kg of LBM was significantly greater in the obese patients.
Author’s Conclusions:
“…obese patients could not effectively use their most abundant fat fuel sources and have to depend on other fuel sources. The nutritional management of obese trauma victims should therefore be tailored towards provision of enough glucose calories to spare protein.”
Evaluation:
This was a small study of heterogeneous trauma patients of varying ages and injuries. Although injury severity score was similar between the groups, in such a small number of patients there remains a high likelihood of other important differences between the groups that could have affected protein breakdown, in addition to BMI status.
An important critique of this study is that protein turnover, lipolysis and fat oxidation was not significantly different between the groups (absolute value or normalized to weight) until they were adjusted for body composition, BUT they never measured the actual body composition of the obese subjects. Instead, the lean mass and total body fat were estimated using body composition values from a completely different set of all male and much younger (average age 24 years) patients, compared to the obese trauma patients (average age 46 years). Obese patients generally have increased calorie expenditure, and have increased amounts of muscle mass compared to lean patients, so it is not surprising that total amounts of muscle degradation or urinary nitrogen losses would be higher as an absolute value.
Perhaps the most important factor of this study for clinicians is that this is not a study of reduced-calorie, extra-protein nutrition support. These trauma patients were evaluated in a completely unfed state, after glycogen stores would be nearly or completed depleted (48-96 hours post trauma). It is not unsurprising that fat metabolism would be compromised in any human that is not yet adapted to ketosis, because efficient fat oxidation requires the presence of carbohydrates. These results would likely have little relevance for critically ill patients who are provided with balanced reduced calorie nutrition that would provide adequate carbohydrate and additional protein.
Several studies have demonstrated that reduced calorie, full protein feeding results in similar nitrogen balance, with some improved clinical outcomes, compared to full calorie feeding in obese patients (1-4). Although weight loss is not necessarily the goal, the available data of reduced-calorie, full protein feeding in obese critically ill patients shows no negative effects, and has the potential benefit of less GI symptoms and improved glucose control generally seen with a modest reduction in calorie provision.
There is a need for larger studies of reduced calorie feeding to help establish guidelines for how large of a calorie deficit is safe, ideal protein goals, and the safe duration of hypocaloric feeding for obese critically ill patients.
If readers are interested in a more in-depth critique of this research, there is an entire paper that provides the full details of the limitations of the research methods published in Nutrition in Clinical Practice in 2005 (5).
Our Take Home Message(s):
1. This small study of unfed obese trauma patients has limited relevance for helping to direct the nutritional care of obese patients who are receiving nutrition support in the ICU.
2. Available data of providing reduced-calorie, full protein feeding to obese patients has demonstrated no negative effects of utilizing endogenous lipid calories, and some potential benefits.
References:
1. Dickerson RN, Rosato EF, Mullen JL. Net protein anabolism with hypocaloric parenteral nutrition in obese stressed patients. Am J Clin Nutr. 1986; 44: 747– 755.
2. Burge JC, Goon A, Choban PS, Flancbaum L. Efficacy of hypocalorictotal parenteral nutrition in hospitalized obese patients: a prospective, double-blind randomized trial. JPEN J Parenter Enteral Nutr. 1994; 18: 203–207.
3. Choban PS, Burge JC, Scales D, Flancbaum L. Hypoenergetic nutrition support in hospitalized obese patients: a simplified method for clinical application. Am J Clin Nutr. 1997; 66: 546–550.
4. Dickerson RN, Boschert KJ, Kudsk KA, Brown RO. Hypocaloric enteral tube feeding in critically ill obese patients. Nutrition. 2002; 18: 241–246.
5. Breen HB. Lipid oxidation and nitrogen balance in critically ill obese patients. Nutr Clin Pract. 2005 Feb;20(1):98-102.
Joe Krenitsky MS, RDN
PS – Please feel free to forward on to friends and colleagues.