Preoperative 4-Week Low-Calorie Diet Reduces Liver Volume and Intrahepatic Fat, and Facilitates Laparoscopic Gastric Bypass in Morbidly Obese


D Edholm, J Kullberg, A Hänni, A Karlsson, A Ahlström, J Hedberg, H Ahlström and M Sundbom


Obesity Surgery, Online First™, 22 December 2010

Patient group:

15 women scheduled for laparoscopic gastric bypass surgery. Average age 34.3 years, average weight 121.3 kg and average BMI 42.9 kg/m2.


Obesity complicates all kinds of abdominal surgery due to decreased intraabdominal space caused by an enlarged liver and increased quantity of intraabdominal fat. Technical difficulty caused by liver enlargement is also one of the most common reasons that a laparoscopic procedure must be converted to open surgery. Successful laparoscopic gastric bypass procedures (GBP) are associated with less postoperative pain, less risk of herniation in the surgical site, improved postoperative pulmonary function and shorter postoperative care than open GBP.

Earlier studies show that a treatment period exclusively with diet replacement can reduce liver size. The aim of this study was to further explore the changes in liver volume and fatty liver in obese patients treated for four weeks on a low calorie diet (LCD) and to determine whether such LCD-induced change facilitates subsequent laparoscopic GBP.


After an initial MRI scan, all patients were treated with LCD (Modifast) for four weeks. The daily ration consisted of four or five bags of Modifast per day, which provided a total energy intake of 800 to 1,100 kcal per day. No additional energy intake was permitted.

After the LCD period, laparoscopic GBP (Roux-en-Y) was performed at the Department of Surgery at Uppsala University Hospital. During the procedure, liver size and shape were assessed, as was surgical complexity.

Results and discussion:

All 15 patients completed the study and lost weight during the LCD period. Average weight loss was 7.5 kg, from 121.3 to 113.9 kg, equivalent to a 6.1% reduction in BMI. The 18 patients in the control group, who ate as usual up to GBP without any specific instructions concerning weight loss, had an average weight of 114.4 kg (BMI 40.8 kg /m2) at surgery. Thus there was no significant difference in average weight between the two groups at the time of surgery.
Liver fat decreased by 40% (p<0.001) after the LCD period. Liver volume decreased by 12% (p<0.001). All patients were able to have laparoscopic GBP; no conversion to open surgery was required. Total score for surgical complexity, based on seven parameters evaluated on a scale from 0 to 2, was significantly lower in the LCD group than in the control group (0.60 vs. 2.22, p<0.05). 

The 12-percent reduction of liver volume achieved after four weeks of LCD shows that the effect of treatment is equivalent to more restrictive diets. The 40-percent drop in liver fat achieved after only four weeks of LCD is consistent with previous observations by Colles et al., who achieved a 43-percent decrease using VLCD, though in that case after a 12-week treatment period.

At time of surgery, body weight of patients in both groups was comparable, but liver assessment and surgical complexity were more favorable in the LCD group. Initial fat mobilization mainly occurs from the liver and intestinal region. One can therefore speculate whether preoperative LCD treatment reduced the typical amount of visceral fat found in a 121-kilogram patient, not just to the level typical for a 114-kilogram patient, but to a level which is normal for a person with much lower body weight. This specific improvement in intraabdominal anatomy could result in a better surgical environment. If the body has not yet had time to adapt to this decrease in volume, there may even be extra space in the abdominal cavity at the time of surgery.

Another interesting finding is that the weight loss that followed in the four weeks after GBP affected only liver volume, not liver fat. The reduction of fat accumulation in the liver is thus accomplished entirely during the LCD-induced weight loss.


The study confirms that moderate preoperative weight loss results in a significant reduction of fat in the liver and liver volume, thereby facilitating laparoscopic gastric bypass. Based on results of earlier studies, as well as the current study, a four-week preoperative LCD period is an effective and feasible treatment which is currently prescribed to all patients scheduled to undergo bariatric surgery at the authors' institution.