Facing surgery is stressful. One thing you can control, however, is how you fuel your body before and after the operation. The right nutrition can reduce muscle loss, support your immune system and help you get back on your feet faster.

In this guide we’ll cover oral nutritional strategies that patients could easily implement prior to and following major surgery to preserve muscle, and minimise atrophy and the resultant loss of functionality. We'll show you the importance of reducing muscle loss, managing insulin resistance, and how to speed recovery through:

•  surgery nutrition
•  preoperative carbohydrate intake
•  best protein intake after surgery
• and give you an easy to follow meal guidance table and timing

Why Nutrition Matters Before and After Surgery

Nutritional status is a strong predictor of postoperative outcomes. Malnourished patients have longer lengths of hospital stay, higher readmission rates, a greater number of complications, and higher mortality risks. Protein intake is especially important for modulating surgical stress and supporting recovery, yet surgical patients significantly under-consume protein, taking in about 22–36% of estimated requirements.

Consequences of malnutrition and inadequate protein intake are more serious for older adults though, due in large part to the challenge of maintaining muscle mass. Malnutrition in older patients leads to rapid deterioration of cardiometabolic health, strength, functionality, independence, and an increased risk of mortality. Nutrition is recognised as an important component of enhanced recovery after surgery, which is designed to minimise stress and facilitate the return of functionality after surgery.

 

What Happens to Your Body After Surgery?

When a person has surgery — even if they aren’t stressed or sick before — the body goes through a series of reactions. These reactions involve inflammation (the body’s natural response to injury), immune system changes, and shifts in how the body uses energy and nutrients. Together, they create a hypermetabolic-catabolic state where the body’s metabolism speeds up and starts breaking down its own tissues to heal.

 

Why Muscle Atrophy Happens After Surgery

After surgery, certain hormones like glucagon and cortisol increase causing significant breakdown of hepatic (liver) and muscle glycogen. These hormones help raise blood sugar and boost the production of molecules that cause inflammation (called proinflammatory cytokines). To provide energy for healing wounds, the body breaks down stored forms of sugar called glycogen, which are found in the liver and muscles.

At the same time, the liver starts making more new glucose (sugar) through a process called gluconeogenesis. This means the liver uses other materials, such as lactate (a byproduct of muscle activity), amino acids (parts of proteins through muscle breakdown), and glycerol (from fat breakdown) to create glucose.

However, because of the high hormone levels, the body becomes less responsive to insulin — the hormone that helps move sugar out from the blood and into cells. This insulin resistance causes blood sugar levels to stay high (a state called hyperglycemia). How long this lasts depends on how serious the surgery is — it can be from a few hours to several days, and sometimes months.

This insulin resistance is a natural part of the stress response to surgery. Even healthy people experience it, but it’s worse for people with diabetes or who already have high blood sugar. If blood sugar levels are not controlled after surgery, it can weaken the immune system and increase the chance of infections or other serious problems.

 

How Fast Is Muscle and Protein Loss After Surgery?

Protein catabolism is elevated during the stress response. The stress from surgery causes a rise in cortisol (a stress hormone), which reduces the body’s ability to build new proteins and increases protein breakdown. As a result, muscles release amino acids. These are sent to the liver to help make glucose, repair wounds, and support the immune system.

Because surgery often means being inactive for a while, muscle loss can be significant. For healthy people, muscle tissue starts shrinking after just 48 hours of immobility, and more so after five days. For example, in young healthy men, the muscles in their thighs got 1.7% smaller after two days without use, and 5.5% smaller after a week — with major losses in key muscles like the quadriceps (front thigh muscles) [1] 

This muscle loss happens even faster in older adults. After knee replacement surgery, older patients can lose about 1% of muscle mass per day, especially in important muscles like the quadriceps and hamstrings. Nearly 80% of this loss happens in the first two weeks after surgery.

 

How Does Muscle Loss After Surgery Affect Strength and Function?

When muscles shrink, strength and ability to do everyday tasks decline. The best way to stop muscle loss is through exercise, especially resistance training (like lifting weights). But since surgery often means you can’t move fully, or at all, right after, muscle loss is hard to avoid.

For example, after only seven days of not moving, young men lost 5.5% of thigh muscle volume, along with decreases in the strength of leg muscles by about 19-21%. Older people lose muscle and strength even faster and have more trouble with activities like standing up from a chair, climbing stairs, walking, or getting up and moving around quickly [2]

The longer someone remains inactive after surgery, the harder it is to recover. After abdominal surgery, it can take around two months to get back full function, and many people who have hip replacements still have difficulty with activities even five years later.

 

How To Prevent Muscle Loss After Surgery

Since exercise isn’t always possible immediately after surgery, nutrition (what and when you eat) is very important. Eating the right kinds of nutrients before and after surgery can help protect muscles, support healing, and improve how well you recover.

Pre and post operative patients need to focus on simple nutritional strategies through diet. It’s important to know how carbohydrates (sugars and starches) and proteins, especially essential amino acids (the building blocks of protein that your body can’t make), can speed healing, reduce muscle loss, and boost recovery outcomes.

 

How Carbohydrates Help Manage Blood Sugar and Insulin Resistance During Surgery

When someone undergoes surgery, the body goes through a lot of stress. During this time, the body’s energy and nutrition needs increase because it’s working harder to heal and fight inflammation. Nutrition around the time of surgery helps by:

•         Supporting these extra energy needs,
•         Helping the body respond better to insulin,
•         And reducing the loss of muscle that can happen after surgery.

Carbohydrates, especially glucose (a simple sugar), play a key role in managing blood sugar and insulin pre and post surgery. Eating carbohydrates before surgery, like a sugary drink 2 hours ahead, can cut the body’s resistance to insulin by up to half. This means the body uses insulin better to process blood sugar. This is important because, as mentioned earlier, surgery often causes insulin resistance, leading to high blood sugar and stress on the body.

Eating carbs the night before and even a few hours before surgery helps keep the protein in the body balanced. This can protect muscle strength, like the muscles in your thighs, which tend to weaken after surgery. Research shows that people who had carbs before surgery lost less muscle strength and recovered it faster over the next 1–2 months compared to those who didn’t.

 

Limits of Carbohydrate-Only Nutrition

However, just eating carbohydrates isn’t enough to support the body's needs during and after surgery because:

1.  Limited Storage: The body can only store enough glucose (in a form called glycogen) for less than a day. Normally, when you fast for many hours, these glycogen stores run low, and the body starts making glucose from other sources like muscles, which isn’t ideal.
2. Not Fully Suppressing Muscle Breakdown: Even with carbohydrate intake, the body still breaks down some proteins (muscle) to make glucose, especially after surgery when the healing process puts stress on the body.
3.  Carbs Don’t Help Insulin Resistance After Surgery: Eating carbs right after surgery doesn’t seem to improve insulin resistance or stop muscles from breaking down proteins.
4.  Carbs Don’t Provide Amino Acids: Glucose doesn’t give the body amino acids, the building blocks of protein, which are very important for healing.

 

The Importance of Protein and Essential Amino Acids for Muscle Health Post-Surgery

After surgery, it’s normal to lose some muscle because the body breaks down muscle protein to get the amino acids it needs. If there isn’t enough protein in the diet, this muscle loss can be worse.

Amino acids, especially essential amino acids (the ones the body cannot make and must get from food), help reduce muscle breakdown by stimulating protein synthesis (building new protein). Studies show that taking essential amino acids can:

 

•         Increase the body’s protein building by 40%,
•         Reduce muscle and overall protein breakdown by 20%,
•         Slow down muscle loss after surgeries like knee or hip replacement,
•         Help muscle strength recover faster,
•         Improve ability to walk, climb stairs, and perform everyday activities, especially in older adults who have weaker muscles.

 

Combining Carbohydrates and Protein for Optimal Surgical Recovery

Both carbohydrates and protein cause insulin to be released, but they affect blood sugar differently:

 

•           Carbohydrates cause a quick rise in blood sugar, which makes the body produce insulin in two phases (a biphasic response). This helps the body store energy but may be less effective if insulin resistance is present, like after surgery or in diabetes.

 

•         Protein raises amino acid levels in the blood, which also triggers insulin release and directly supports muscle building. Unlike carbs, the insulin response from protein isn’t harmed by insulin resistance.

 

Eating both carbs and protein together before surgery can reduce muscle loss and help maintain strength. After surgery, taking free essential amino acids or a high protein supplement, along with normal dietary protein, could provide a quick boost of amino acids to start muscle building, followed by a steady supply to continue healing and support the body’s needs.

Timing is important too; different types of carbs and protein should be chosen depending on how close it is to the surgery (weeks, days, or hours before and after) to get the best benefits.

Best Timing and Sources of Carbohydrates and Protein Around Surgery

Nutrient timing strategies can be implemented during both the pre- and post-operative periods to prepare the body for the stress of surgery, support increased metabolic demands, and offset the catabolic consequences. The goal of pre-operative nutrition is to ensure adequate energy stores to meet the demands of the stress state. The goal of post-operative nutrition, on the other hand, is to promote nitrogen balance, reduce the loss of lean mass, and facilitate rapid healing and recovery.

As our understanding of gastrointestinal motility, the harmful effects of long fasting periods on metabolic stress, insulin sensitivity, and recovery have improved, pre-surgical fasting recommendations have been revised. According to ERAS (Enhanced Recovery After Surgery) protocols, it is currently recommended that patients fast for 6 h following a light meal, and for 2 h from consumption of clear liquids prior to surgery.

Substantial developments in dietary and sport supplements provide significant opportunity to maximize nutritional intake during the immediate hours before and after surgery and should be given consideration for pre- and post-surgical nutrition. Oral nutritional supplements have also been shown to reduce the net cost associated with hospitalization. Cost savings are associated with reduced complications (−35%) and length of stay (−2 days).

 

Best Nutritional Protocol Pre-Surgery

Key Takeaways:

Start nutrition optimisation 7–10 days before surgery with a focus on high-quality carbohydrates and protein.

Emphasise complex carbohydrates (vegetables, fruits) for energy, vitamins, minerals, fiber, immunity, and gut health.

Consume 1.2–2.0 g/kg/day of high-quality protein, spread evenly in 20–40g servings throughout the day, prioritising animal sources (chicken, beef, fish, eggs, milk, cheese, hydrolysed collagen) for best amino acid profile and absorption.

Follow fasting guidelines strictly but adapt nutrient form: stop whole foods 6 hours before surgery but continue clear liquids with carbs and protein until 2 hours before surgery.

Use supplemental protein and carbohydrates (40up protein shakes, sports drinks, chocolate milk) in the hours before surgery for easy digestion and stable energy.

Consume ~50g of carbohydrate 2 hours pre-surgery (like clear fruit juices, without pulp, such as apple or cranberry) to maintain blood glucose and reduce surgery stress.

Take free-form essential amino acid (EAA) supplements or 40up protein shake 2 hours pre-surgery to boost protein synthesis and overcome muscle anabolic resistance effectively.

Pre Surgery Timeline and Meal Guidance Table

Time Before Surgery	What to Eat/Drink	Why
7–10 days before surgery	- Complex carbs: vegetables, fruits, whole grains (about 60% calories or 8 g/kg/day carbs) - High-quality protein: 1.2-2.0 g/kg/day from animal sources, distributed in 20-40g servings Protein shakes eg: 40up	Maximise glycogen stores for energy, ensure vitamin/mineral intake, enhance immunity, and build muscle protein reserves.
Evening before surgery	- Quality meal high in complex carbs and protein (chicken, fish, eggs, whole grains, vegetables)	Starts the final carbohydrate loading and protein replenishment before fasting begins.
Morning of surgery (if surgery is later in day)	Light breakfast with complex carbs + high-quality protein (small portion) + 40up protein shake	Supports energy stores and optimal amino acid status without excess intake before fasting window.
6–12 hours before surgery	Well-rounded meal with complex carbs + high-quality protein or try 40up protein shakes/sports drinks if near 6 hours	Ensures nutrient stores, easier digestion when closer to fasting onset.
Within 6 hours before surgery	Stop whole foods; consume protein + carbohydrate beverages (40up protein shakes, sports drinks, chocolate milk). Modified starches recommended for steady glucose.	Avoids stomach content for anesthesia safety while maintaining metabolism and reducing insulin resistance.
2 hours before surgery	- Consume ~50g carbohydrate - Take free-form EAA supplements	Maintains blood glucose levels to reduce surgical metabolic stress and promotes anabolic protein balance before surgery.
Fasting starts 2 hours before surgery	Only water or clear liquids allowed	Ensures safe anesthesia and reduces aspiration risk.

 

Why This Protocol Matters

1.           Energy and glycogen storage: Carbohydrates fill glycogen stores, important for energy during and after surgery.
2.           Muscle preservation: Adequate protein intake stimulates muscle protein synthesis, combats muscle loss, and helps with recovery.
3.           Immune support: Complex carbs provide fiber and micronutrients that support the immune system and gut microbiota.
4.           Metabolic stability: Pre-surgery carbs and EAAs reduce insulin resistance and mitigate the stress response caused by surgery.
5.            Safe fasting: Updated fasting guidelines allow some nutrient intake closer to surgery to avoid prolonged fasting harms.
6.            Improved recovery: Nutrition optimisation helps reduce complications, speeds healing, and decreases hospital stay.

Summary

Nutrition Aspect	Timing	Example Foods/Supplements	Purpose
Carbohydrates	7–10 days before	Vegetables, fruits, whole grains	Maximise glycogen, immunity
Protein (animal-based)	Daily, in 20–40 g servings	Chicken, beef, fish, eggs, milk, cheese, hydrolysed collagen	Muscle building, anabolic response
Whole food meal	Evening before surgery (+ breakfast if later day surgery)	Balanced complex carbs + protein meal	Last major nutrient intake
Protein & Carb drinks	Up to 6 hours pre	40up protein shakes, chocolate milk, sports drinks	Easy digestion, maintain energy
Free-Form EAAs	2 hours pre	40up protein shake or EAA supplement powders	Maximise protein synthesis
Fasting  6 hours (solid food),	2 hours (clear liquids) before surgery	No food, only water/clear liquids	Safety for anesthesia

 

This protocol ensures patients are nutritionally prepared to handle the stress of surgery with improved energy availability, protein reserves for healing, and minimal metabolic disruption from fasting.

 

The Best Post-Surgery Nutritional Protocol: What, When, and Why

Key Takeouts:

Early post-surgery: Appetite is suppressed; solid food intake is difficult.

40up protein shake or Free form Essential Amino Acids (EAAs): Ideal immediately post-surgery to support healing without affecting appetite.

Transition phase: Move from EAAs and continue protein shakes as appetite improves.

Protein intake goal: 1.6 to 3.0 g/kg/day, distributed evenly (20–40 g protein per meal).

Use supplements (EAAs/40up protein shake) between meals if appetite is low.

Nutrient timing around rehabilitation: Proper meals before, during, and after therapy aid recovery.

Nutrition Timeline & Content

Timeline	What to Eat/Consume	Why It’s Important
Immediately post-surgery (0-24 hours)	- 40up protein shake or Free form EAAs (amino acid supplements) in small amounts - Avoid heavy solid foods	Appetite often suppressed - 40up protein shake supply vital amino acids and hydrolysed collagen for healing - EAAs don’t reduce appetite or stress insulin response - Supports immune function and tissue repair without gastric discomfort
Next few days (1-3 days post-op)	- Protein beverages (40up protein shakes) with higher calorie content - Gradual reintroduction of soft, whole foods as tolerated	- Provides more calories and protein as appetite improves - Supports anabolic (muscle-building) processes - Easier digestion than solid foods initially
Rehabilitation period (starting days 3–7+)	- Total protein intake: 1.6 - 3.0 g/kg/day distributed evenly - 20-40 g protein per meal, 3-5 times daily - EAA/protein supplements between meals if appetite reduced - Nutrient timing around rehab sessions:    • 3–4 hours before: small meal with 50-100 g complex carbs + 30-40 g quality protein    • 15–45 minutes before therapy: carbohydrate + protein beverage    • After therapy: protein beverage	- Enhanced muscle protein synthesis and strength recovery - Optimal energy and nutrient supply for exercise performance - Better functional recovery and faster return to daily activities
Throughout recovery	- continue 40up protein shakes with balanced nutritious meals	- May enhance muscle strength, function, reduce inflammation, and support gut health

 

Why This Nutritional Approach Is Important

• Early amino acid supply is critical to jump-start healing and immune responses even when the patient cannot eat solid foods.
• Maintaining high protein intake throughout recovery is essential to prevent muscle loss and promote tissue repair.
• Nutrient timing around rehabilitation sessions ensures muscles have the fuel to perform and recover.
• Supplements can enhance muscle recovery and overall well-being, especially in older patients or those undergoing intense rehab.

Post Surgery Nutritional Summary

•          Start with 40up protein shake or free form EAAs immediately after surgery to supply needed amino acids without burdening digestion or appetite.
•          Continue protein shakes and gradually reintroduce soft foods based on appetite.
•          Aim for 1.6 - 3.0 g/kg/day protein, spaced evenly, using supplements if full meals are not possible.
•         Plan balanced pre-, during-, and post-rehabilitation nutrition to support exercise and recovery.
•         Consider supportive nutritional supplements to enhance muscle recovery and immune health.

This comprehensive nutritional approach leveraging preoperative carbohydrate loading combined with postoperative protein and amino acid supplementation most effectively supports recovery by mitigating insulin resistance, preserving muscle mass and function, and optimising metabolic health around surgery.

This article references information contained in the clinical review ‘Pre- and Post-Surgical Nutrition for Preservation of Muscle Mass, Strength, and Functionality Following Orthopedic Surgery’ published in the Journal of Nutrients 2021.

Considerations provided within this article are meant to compliment, not replace current peri-surgical recommendations, as outlined by governing organizations, and patients should always consult with a physician/nutritionist team for individualized recommendations