Carb loading is a planned surge of high-carb meals to pack muscles with glycogen. In bodybuilding it’s a peak-week tactic to make muscles look fuller and harder.

This full guide unpacks the strategy from every angle: what carb loading really is, when to carb load before a bodybuilding competition, how to do it step-by-step, the benefits and risks, and the best foods to use for maximum effect!

What is Carb Loading?

Carbohydrate loading (commonly known as carb loading) is when bodybuilders and endurance athletes eat a high number of carbohydrates in a single day or over a series of days in preparation for a competitive event.

Conceptually, carb loading is the same for endurance athletes (runners, cyclists, etc) and bodybuilders. It’s about planning periods of high carb and low carb intake to balance energy stores. However, each group has a drastically different reason for loading up.

For endurance sports, it delays fatigue, but for carb loading bodybuilding athletes, it makes muscles appear bigger and harder on stage.

Ultimately, carb loading is less about “eating tons of pasta” and more about timing carbohydrates so they deliver maximum performance or aesthetic payoff when it matters most.

Benefits of Carb Loading

Carbohydrates are macronutrients that serve a very important function in your body: They are the body’s main energy source. Your body breaks down carbohydrates into sugar that enters your bloodstream and gets stored for energy use in your muscles and liver as glycogen. Your muscles usually only store small quantities of glycogen. And when you exercise, you deplete your energy storage.

In men, a carbohydrate-loading diet can raise glycogen storage levels in your muscles from 25 to 100 percent of their normal amount. Studies on carbohydrate loading in women have shown mixed results – women may need to take in more calories than men during carbohydrate loading to experience the same gains in glycogen.

So theoretically, the reasons certain people carb load are either because they want to:

1. “build up” stores of glycogen so they can use this extra energy storage to help improve endurance during long sessions.

2. Fill their muscle with glycogen so they pull water into the muscle, helping them gain mass and a fuller muscle appearance.

Additional benefits of carb loading include:

• Super-charged energy reserves – Bigger glycogen stores mean a stronger start and fewer late-race slowdowns.

• Noticeable performance edge – Marginal increase in muscle girth can influence judging.

• Supports repeated high-intensity bursts – Useful not just for steady endurance but also for sprint intervals, heavy sets, or last-minute finish surges.

• Psychological lift – Knowing you’re fully fueled—or stepping onstage looking pumped—can heighten confidence and focus when the pressure is on.

Key Takeaway: Whether your goal is lasting stamina or a sharper physique, strategic carb loading can translate stored carbs into real-world performance and aesthetic gains— when timed and executed correctly.

Who is Carb Loading for?

As we mentioned, carb loading is a strategy employed mainly by two groups of elite athletes:

1. Endurance athletes, who use it to help them increase their energy storage for long runs, bike rides, swims, etc. For these types of athletes, when timed effectively, carb loading has been shown to increase muscle glycogen, which can, in turn, lead to improved performance.

2. Bodybuilders and fitness athletes, who use carbo-loading to gain size and mass before bodybuilding competitions. However, some researchers advise exercising caution. A paper published in the Journal of the International Society of Sports Nutrition stated that “If carbohydrate loading is utilized, a trial run before competition once the competitor has reached or nearly reached competition leanness should be attempted to develop an individualized strategy.” In other words, the timing and efficacy of a carb loading vary greatly from person to person. Make sure to experiment before the next big bodybuilding competition.

How to carb load: Step by Step Guide

How you carb load will depend on what you’re trying to accomplish.

Bodybuilders and fitness competitors

Bodybuilders handle carb loading differently from endurance athletes because their goal is visual, not aerobic: they want muscles that look round, dense, and vein-popping on contest day.

Because every physique responds a little differently, think of the protocol below as a template—then rehearse it during prep so you learn exactly when to carb load before a bodybuilding competition and how many grams your body can handle.

• Timing (test first): Start the load 2–3 days before show or photo shoot; repeat a “practice peak” a few weeks out so you can fine-tune the schedule.

• Carb target: Follow Jim Stoppani, Ph.D.’s guideline of 3–4 g carbs per pound of body-weight (≈ 6.6–8.8 g/kg) spread over 4–6 meals.

• Protein, fat, and fluids: Keep protein steady (~1 g/lb) to protect muscle; keep fats under 20 % of calories so most intake goes to carbs.

• Water intake: Maintain normal sodium and sip water steadily. Only consider modest fluid adjustments in the final hours if tested safely beforehand—and ideally under professional supervision.

• Final top-off (60–90 min pre-stage): Many bodybuilders use 25–50 g of fast-digesting carbs to push vascularity without adding gut bulk. For example, a couple of plain rice cakes topped with honey and a small pinch of salt are a common choice.

Endurance athletes

Endurance athletes use carb loading to hit the starting line with every last gram of glycogen topped up, because once those stores are full, fatigue sets in later and pace stays steadier. Unlike bodybuilders—who load for appearance—you’ll be running, riding, or swimming long enough to burn through that energy, so the goal is maximum storage first, then steady refueling on the course.

• Start the load 48–72 hours before the event: Taper training volume while you ramp up carbs; the lighter workouts help funnel more glucose into muscle.

• Hit the carb target: 4–7 g of carbs per pound of body weight (≈ 9–15 g/kg) each day. A 150 lb runner would aim for 600–1,050 g daily.

• Pre-race boost: A high-carb meal (~2 g carbs/lb) 3 hours before the gun can lift muscle glycogen another ~15%. Many athletes consume ~12–16 oz of electrolyte beverage pre-race, though individual needs may vary based on sweat rate and conditions.

• Fuel during the event: Take 30–60 g of carbs per hour from gels, sports drinks, chews, fruit, or even candy to keep blood glucose steady and delay fatigue. Practice this in long training sessions.

• Immediate post-race meal: Within 60 minutes, eat a carb-rich meal or shake (1–1.2 g carbs/kg) plus some protein to jump-start glycogen re-synthesis and recovery.

• Hydration, sodium, and rest: Keep fluids and electrolytes steady all week; dehydration blunts glycogen storage. Prioritise sleep—your body does most of its glycogen packing and muscle repair overnight.

Best Foods for Carb Loading

The ideal food choices differ slightly for physique athletes versus endurance racers, but the guiding principle is the same: pack the most glycogen with the least digestive drama.

Here are some nutritious foods high in carbohydrates:

Side Effects and Risks of Carbo Loading

As we’ve seen, carb loading may help you, increase your glycogen levels, increase endurance and mass, and improve performance. However, carb loads aren’t effective for everybody.

Whether you’re a triathlete or aspiring bodybuilder, other factors come into play that may impact your athletic performance and/or the effectiveness of your carb-load strategy (e.g., your current fitness level, how much water you drink, and the intensity of your exercise sessions).

Carb loading isn’t a silver bullet against muscle fatigue … if you run/bike/swim for over 2 hours straight you’re going to get tired.

There are some inherent risks that come with eating mass quantities of any macronutrient, including carbohydrates. You may experience side effects such as:

• Rapid weight gain: Each gram of glycogen stores roughly 3 g of water, so the scale can jump 2–4 lb (1–2 kg) within a day. Fine for bodybuilding stage fullness, but it can feel sluggish if you mis-time it for endurance.

• GI distress (bloating, cramping, gas): Large, unfamiliar carb loads—especially from high-fiber or high-fat foods—slow gastric emptying and invite mid-race bathroom stops.

• Blood-sugar swings: Sharp rises and falls in glucose may leave you light-headed; athletes with diabetes or pre-diabetes should carb load only under medical guidance.

• “Spill-over” look for bodybuilders: Overshooting carbs or cutting water/sodium too aggressively can blur definition instead of tightening it.

• False sense of invincibility: Glycogen can carry you further, but it cannot offset poor pacing, inadequate electrolytes, or lack of sleep.

Bottom line: Carb loading can amplify endurance and produce a fuller stage physique, yet it isn’t risk-free or one-size-fits-all. Test the protocol well before race day or contest peak, listen to your gut (literally), and adjust volume, food choices, and hydration to your own physiology.

Summary

Carb loading is a dietary strategy that can yield better results for endurance athletes, bodybuilders and fitness competitors.

However, we should note that carb-restricted, high protein diets have been shown to be the most effective for decreasing fat mass while simultaneously increasing lean muscle mass (which is the goal of most of our readers).

If weight loss or fat loss is your goal, a low carb diet might be better for you.

But if you are a runner looking for a boost in your next race or a bodybuilder looking to make noise in the world of bodybuilding, carb loading may be right for you.

FAQs

When to carb load before a bodybuilding competition?

Most physique athletes start 48 – 36 hours out and finish 12 – 24 hours before stage time. Run a “dress rehearsal” during prep to fine-tune the exact window for your body.

What are the best foods for carb loading on race week?

White rice, pasta with light sauce, plain bagels, pancakes, sports drinks, honey-topped rice cakes, and ripe fruit all deliver rapid carbs with minimal digestive stress.

Does carb loading make you gain fat?

Short-term weight gain (2 – 4 lb / 1 – 2 kg) is almost all water bound to glycogen, not fat. Significant fat gain is unlikely during short-term loading unless total caloric intake remains elevated over multiple days.

Can women carb load the same way men do?

Women can benefit, though some may require slightly more carbohydrate per kg of body weight to achieve similar glycogen increases. Test your own protocol well before race or show day.

Is carb loading risky for people with diabetes or pre-diabetes?

Large swings in blood glucose can be problematic. If you have any glucose-management issues, consult a healthcare professional before attempting a high-carb load.
***

Scott Christ is a health and wellness entrepreneur, writer, and website strategy consultant. He’s also the creator of the world’s healthiest plant-based protein powder.