I don't have a comprehensive answer for that, but sometimes diabetes sneaks up on you along with pancreatic cancer. It's worth getting checked for if you don't already know your status. It takes a fine balance of enzymes and insulin for your body to get proper nutrition out of the foods you eat. I lost about 15 pounds (from 175 to 160) after Whipple, but that's where I wanted to be anyway.

While on Folfirinox, I regained the 30 pounds I had lost prior to diagnosis, so I had pounds to spare at that point. Since losing the 15 pounds post-Whipple, I've been stable as a rock at 160. I'm eating a LOT of calories every day, which would probably be fattening me up a good bit more if I had a full, functioning pancreas.

It took almost two years to stabilize my weight. I eat a lot, focus on protein, and (think) I have my creon and insulin dosing figured out. I gained weight very slowly, but I did it. A dietician can help advise you.
Good luck, best wishes!

The Whipple procedure involves the resection of the head of the pancreas. This section is where up to 82% of the acinar cells are found whose function is to produce and secrete the digestive enzymes amylase, lipase and protease. These enzymes are essential to digest carbohydrates, fats and proteins respectively so that nutrients and vitamins are absorbed through the small intestine. When there is insufficient enzymes available, the condition of Exocrine Pancreas Insufficiency (EPI) results. It is ameliorated using Pancreatic Enzymes Replacement Therapy (PERT). This is accomplished with Rx pancrealipase-a generic name of a blend of the three digestive enzymes taken at the start of the meal and if additional capsules are required, taken staggered throughout the course of the meal to ensure sufficient levels of enzymes are present for thorough digestion.

Some patients don’t require PERT but almost 50% do to some degree either short or long term. There are some overt symptoms that warrant going on PERT. When just weight loss is the symptom, the fecal elastase is used to make a diagnosis.

I had suffered significant weight loss after the Whipple procedure resulting from EPI. My surgeons never prescribed PERT, telling me instead to eat smaller meals less frequently. That did not work even with increasing caloric intake. I had to advocate in requesting a pancrealipase be prescribed. The effects were immediate…it stopped GI discomfort and I gained 10 lbs in 16 days. I optimized the dosage based on the type of meals and fat content and my weight and BMI has returned to what is considered a healthy weight for my height.

The most knowledgeable team member to address EPI is a registered dietitian. Look for one with the designation C.S.O. (Certification Specialist Oncology). They are connected with GI Cancer, Hepatobiliary and Pancreas programs at large comprehensive cancer centers. They have advanced training and extensive knowledge in the dietary and nutritional needs of Whipple patients. My quality of live, stamina and strength significantly improved once I began PERT.

Some links on PERT-

Pancreatic Enzymes
https://letswinpc.org/managing-pancreatic-cancer/2019/10/09/pancreatic-enzymes-explained/

@montyd, along with the helpful advice you've already received, you might also find some additional tips in this related discussion:
- Weight Loss after Whipple: What strategies helped you?
https://connect.mayoclinic.org/discussion/weight-loss-after-whipple-performed-on-2242022/

I am also 4’11” and find it hard to put the weight back on! Got down to 98 lbs and felt awful. High protein and frequent mini-meals seem to help. I supplement with protein shakes but avoid excess sugar also. Make sure you choose nutrient dense foods, if possible.
I was diagnosed with Stage 4 PanCan mid-July of 2022, had Whipple surgery within three weeks, did a full (12) course of chemo (Fulfirinox ?) with most doses reduced by 80%, had 6 glorious months without chemo, now halfway through Abraxane/Gem.. My bloodwork shows high levels of toxicity now. C19-9 marker shows improvement and PET scan will be repeated soon. It’s always a race to see what will get me, the chemo or the cancer? I took a two week break over the holidays to be with my family and I got the chemo scheduled every two weeks instead of weekly. I’ll try that.
Please remember that YOU are in charge and will make the important decisions in connection with your doctors. They will advise but we can stop treatment or change it at any time. I clean out my things, make final plans, research Hospice care, etc. Now while I can! I view 18 months after a Stage 4 diagnosis as a gift each day!!