According to Gram Research analysis, a new ERAS-based nutrition protocol for knee replacement surgery reduces nausea after surgery from 19% to just 4% and helps patients maintain better protein levels, while allowing them to drink fluids only 2 hours before surgery instead of 7 hours. A 2025 prospective study of 96 knee surgery patients found that the optimized nutrition approach improved patient satisfaction and preserved nutritional status without increasing bleeding or hospital stay length, suggesting hospitals should reconsider traditional fasting rules for this common procedure.
A new study shows that patients preparing for knee replacement surgery benefit from a special nutrition plan that lets them eat and drink closer to surgery time. Instead of fasting for many hours, patients on the ERAS nutrition protocol drank fluids just 2 hours before surgery and ate light meals the night before. This approach helped patients maintain better protein levels after surgery, experienced less nausea, and reported higher satisfaction with their care. The findings suggest hospitals should reconsider traditional fasting rules for knee surgery patients.
Key Statistics
A 2025 prospective comparative study of 96 knee replacement surgery patients found that an ERAS-based nutrition protocol reduced postoperative nausea from 18.75% to 4.17%, a reduction of more than 75%.
According to a 2025 study published in Frontiers in Nutrition, patients on the ERAS nutrition protocol for knee surgery maintained significantly higher protein levels on day 3 after surgery, averaging 139.29 mg/L compared to 125.31 mg/L in the traditional fasting group.
A 2025 research study of 96 knee replacement patients found that the ERAS nutrition protocol reduced fluid fasting time from over 7 hours to just 2 hours before surgery without increasing blood loss or extending hospital stays.
In a 2025 prospective study, patients following the ERAS nutrition protocol before knee replacement surgery reported significantly higher satisfaction with their care compared to those using traditional fasting approaches.
The Quick Take
- What they studied: Whether a new eating and drinking plan before knee replacement surgery helps patients recover better and feel less sick after the operation
- Who participated: 96 patients having total knee replacement surgery at a hospital in China between January and December 2025. Half followed the new nutrition plan, and half followed the traditional fasting approach
- Key finding: Patients on the new nutrition plan drank fluids only 2 hours before surgery instead of 7 hours, had better protein levels after surgery, and experienced nausea in only 4% of cases compared to 19% in the traditional fasting group
- What it means for you: If you need knee replacement surgery, ask your surgeon about the ERAS nutrition protocol. It may help you feel better after surgery with less nausea, though more research is needed to confirm these benefits apply to all patients
The Research Details
Researchers divided 96 patients into two groups based on when they arrived at the hospital. One group (48 patients) followed the traditional approach of fasting for many hours before surgery. The other group (48 patients) followed a new ERAS nutrition plan that allowed them to drink clear fluids up to 2 hours before surgery and eat light meals the night before. The ERAS protocol is a set of evidence-based practices designed to help patients recover faster from surgery by changing how they prepare and what happens during their care.
The study measured several important things: protein levels in the blood after surgery, how much nausea patients experienced, how satisfied patients were with their care, and how long they had to fast. Researchers also checked for complications like bleeding and how long patients stayed in the hospital.
This type of study is called a prospective comparative study, which means researchers followed patients forward in time and compared two different approaches. While this design is useful for getting initial evidence, it is not as strong as a fully randomized trial where patients are randomly assigned to groups
The way hospitals prepare patients for surgery has been based on old rules that required long fasting periods. These rules were created to prevent a rare but serious complication during anesthesia. However, newer research suggests that shorter fasting times may be safe and could actually help patients recover better. This study tests whether a modern nutrition approach works for knee surgery patients, which is important because knee replacements are very common procedures
The study has some strengths: it measured important health outcomes, included a reasonable number of patients, and compared two clearly different approaches. However, the study also has limitations. Patients were not randomly assigned to groups, which means the groups might have been different in ways that affected the results. The study was conducted at a single hospital, so results may not apply everywhere. The researchers acknowledge these limitations and call for larger, more rigorous studies to confirm the findings
What the Results Show
The main finding was that patients on the ERAS nutrition plan had better protein levels after surgery. On day 3 after surgery, the nutrition group had an average protein level of 139.29 mg/L compared to 125.31 mg/L in the traditional fasting group. This difference was statistically significant, meaning it was unlikely to happen by chance.
Patients on the nutrition plan also had much shorter fasting times for fluids. They waited only about 2 hours before surgery compared to over 7 hours in the traditional group. This shorter fasting time did not cause any safety problems.
One of the most noticeable benefits was a reduction in nausea after surgery. Only 4.17% of patients in the nutrition group experienced nausea and vomiting compared to 18.75% in the traditional fasting group. This is a meaningful difference that would make surgery recovery more comfortable for patients.
Patients in the nutrition group also reported higher satisfaction with their care overall. There were no differences between groups in blood loss, fluid drainage from the surgical site, or how long patients stayed in the hospital
The study also measured inflammation markers in the blood, though these did not show significant differences between groups. The nutrition group maintained better protein levels even before surgery, suggesting the protocol helped preserve the body’s nutritional reserves. The research team created a statistical model that confirmed the nutrition intervention independently reduced nausea risk, even when accounting for patient age
This study aligns with a growing body of research showing that modern fasting guidelines are safer and more beneficial than traditional long fasting periods. The ERAS protocol represents a shift in surgical care toward evidence-based practices. Previous studies in other types of surgery have shown similar benefits from shorter fasting times, so this knee surgery study adds to that evidence. However, most previous research has focused on other surgical procedures, making this knee replacement study a valuable addition
The study used quasi-randomization, meaning patients were assigned to groups based on admission order rather than true random assignment. This could introduce bias if patients admitted at different times were different in important ways. The study was conducted at a single hospital in China, so results may not apply to all populations or healthcare settings. The follow-up period was relatively short, so the study does not show whether benefits persist weeks or months after surgery. The study did not measure functional outcomes like how well patients could walk or move their knee after recovery. The researchers acknowledge these limitations and recommend larger, more rigorous studies with longer follow-up
The Bottom Line
If you are scheduled for knee replacement surgery, discuss the ERAS nutrition protocol with your surgical team. Ask whether your hospital uses this approach and whether it is appropriate for your situation. The evidence suggests it is safe and may reduce nausea and improve recovery, but individual circumstances vary. This recommendation has moderate confidence based on a single study; stronger evidence would come from larger trials
Patients scheduled for total knee replacement surgery should care about this research, as it directly applies to their preparation and recovery. Surgeons and anesthesiologists should consider adopting these protocols. Patients with certain medical conditions, allergies, or complications may need modified approaches, so individual discussion with your medical team is essential. This research is less relevant to patients having other types of surgery, though similar protocols may apply
Benefits appear quickly. Patients reported less nausea immediately after surgery, and protein levels improved within the first 3 days. Most patients go home within a few days of knee replacement surgery, so the benefits during this critical early recovery period are most relevant. Longer-term benefits like improved walking ability and knee function would require extended follow-up studies
Frequently Asked Questions
Can I eat or drink before knee replacement surgery?
The ERAS protocol allows clear fluids up to 2 hours before knee surgery and light meals the night before, compared to traditional fasting of 7+ hours. A 2025 study found this approach is safe and reduces nausea from 19% to 4% after surgery. Always follow your surgeon’s specific instructions
Does eating before surgery increase nausea and vomiting?
No, research shows the opposite. A 2025 study of 96 knee surgery patients found that the ERAS nutrition protocol, which allows eating and drinking closer to surgery time, actually reduced nausea and vomiting to 4% compared to 19% with traditional fasting
What is the ERAS protocol for surgery?
ERAS stands for Enhanced Recovery After Surgery. It is a set of evidence-based practices that change how patients prepare for and recover from surgery. For knee replacement, the ERAS nutrition protocol allows shorter fasting times and optimized nutrition to help preserve protein levels and reduce complications like nausea
How long do I need to fast before knee replacement surgery?
The ERAS protocol recommends fasting from solid food for about 6 hours and from clear fluids for only 2 hours before knee surgery. A 2025 study found this shorter fasting time is safe and helps patients recover better with less nausea compared to traditional 7+ hour fasting
Does better nutrition before surgery help you recover faster?
Yes, a 2025 study of 96 knee surgery patients found that the ERAS nutrition protocol preserved protein levels better after surgery and reduced nausea significantly. While hospital stay length was similar, patients reported higher satisfaction and experienced fewer complications
Want to Apply This Research?
- Track nausea levels and pain scores for the first week after surgery using a daily 0-10 scale. Record what you ate and drank before surgery and note any side effects. This helps you and your doctor understand how the nutrition protocol affected your individual recovery
- Work with your surgical team to plan your pre-surgery meals and fluids according to the ERAS protocol. Set phone reminders for your fasting cutoff times. Prepare approved foods and drinks the day before surgery. Log your pre-surgery nutrition in the app to ensure you follow the plan correctly
- Use the app to track daily nausea, pain, appetite, and energy levels for at least 2 weeks after surgery. Compare your recovery timeline to typical recovery expectations. Share this data with your surgeon at follow-up appointments to help them understand how the nutrition protocol worked for you personally
This article summarizes research findings and is not medical advice. The ERAS nutrition protocol may not be appropriate for all patients or all surgical situations. Individual medical conditions, allergies, and complications may require different preparation approaches. Always follow your surgeon’s and anesthesiologist’s specific instructions for your surgery. Do not change your fasting or eating plans before surgery without explicit approval from your surgical team. This research comes from a single hospital study with a quasi-randomized design; larger, more rigorous studies are needed to confirm these findings apply broadly. Consult your healthcare provider before making any changes to your surgical preparation
This research translation is published by Gram Research, the science division of Gram, an AI-powered nutrition tracking app.