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The Ketogenic Diet for Bodybuilders

Author: Jeb Roberts, MA; Photographer: Paul Buceta; Model: IFBB Pro Lee Banks

Mention ketogenesis to most bodybuilders, and you’ll be met with either a blank stare or a rant about low-carb diets. Complaints range from complete lack of energy (After a week I couldn’t get my ass off the couch!) to total disregard for health (Isn’t that a high-fat diet? What about your heart?). But what you’ll rarely find amidst the warnings is a reliable definition of the diet and how it’s achieved. So why is this misunderstood method still kicking around after 90 years? Because despite the myths and misconceptions that surround it, it works — both reliably and quickly.

We’ve all heard the party line when it comes to fat loss: Keep caloric intake below caloric expenditure, kick fatty foods to the curb, and crush the cardio every day after work until you’ve seen every episode of Seinfeld at least twice from a treadmill. But what happens when you toe the line, put in the work and stop seeing results? Or, more accurately in most cases, what recourse do you have when the established fat-loss wisdom gets you only 90% of the way there? The answer, for bodybuilders or anyone who’s simply hell-bent on being beach ready, is to push fat loss into overdrive with a little help from the ketogenic diet.


What Is Ketosis?


While many might use the terms “ketogenic” and “low-carb” interchangeably, not all low-carb approaches are as extreme — or as effective — as the ketogenic diet. “Technically, a ketogenic diet refers to any diet that contains fewer than 100 grams of carbohydrate per day,” says Lyle McDonald, CSCS, who literally wrote the book on The Ketogenic Diet, and who’s spent years researching the ins and outs of ketogenesis for bodybuilders and other athletes. The ketogenic diet was first formalized in 1921 as a treatment for childhood epilepsy, and though numerous studies have proven its effectiveness for that purpose, researchers over the years have also noticed that the diet has a pronounced impact on fat loss. Whereas other so-called low-carb diets, like the Zone, call for macronutrient ratios of up to 40% carbohydrate, the ketogenic diet favors the extreme low-carb range, filling in the rest of a dieter’s calories with high protein and moderate fat. The goal of this approach, according to McDonald, is for the bodybuilder to derive energy by burning ketones in place of carbs.

“Ketosis occurs when the body starts producing ketones — a byproduct of fat metabolism in the liver — in a high-enough concentration that the ketones start being used for fuel instead of carbohydrate,” McDonald says. These ketone bodies can be thought of as nature’s back-up plan. In times of starvation — when a human consumes little or no carbohydrate for energy — the body turns to plan B and converts stored fat to ketones for energy purposes, which the body can burn in place of carbs. “Ketones are produced almost exclusively in the liver when fat oxidization, or burning, is ramped up to high levels due to low carbohydrate intake,” McDonald says. “These ketones then play a number of roles in the body. Perhaps the most important, in terms of dieting, is that they can replace glucose as a fuel in tissues such as skeletal muscle, liver, and to some degree, the brain.”

But while the evolutionary purpose of ketogenesis might be to keep you alive and functioning during times of starvation, the process has practical benefits for bodybuilders looking to cut fat in a world of excess. According to McDonald and other ketogenesis experts, the ketogenic diet burns fat more quickly and effectively than any other method for most people. Even better, studies have shown that the diet serves as a natural appetite suppressant, and while it won’t necessarily support muscle growth, it helps bodybuilders maintain maximum muscle during cutting phases. “As long as protein is sufficiently high and training is kept low-volume and heavy, muscle loss won’t occur in ketosis,” McDonald says. “There’s a rapid water and glycogen loss that occurs in ketosis, and it can make people feel flat and stringy — they think they’re losing muscle when they aren’t. But as soon as they replenish carbs, they’ll blow up.” Naturally, these benefits are available only to bodybuilders who master the ins and outs of this occasionally complex method, so you’ll need to pay close attention to your body’s signals as you carve a path to ketogenic fat loss.


Reaching Ketosis


While the rest of the world frets over dietary fat intake in a futile effort to shed pounds, bodybuilders have long known that managing carbs is the real key to getting cut. It therefore makes sense that many bodybuilders, whose goal is to showcase every shredded sinew, eventually gravitate to the lowest of low-carb approaches. Though there are varying degrees of ketosis, McDonald recommends that first-timers start by aiming for 100 grams of carbs a day and filling in the rest of their protein and dietary fat according to their needs. Like most other trainers, he suggests at least 1–1.5 grams of protein per pound of lean body mass, though he concedes that protein can be a limiting factor in dieters who are trying to stay ketogenic. “Protein can impact the development of ketosis, since about half of dietary protein can be converted to glucose,” he says. “But even if it limits ketosis, it’s still more important to get adequate protein to avoid muscle loss.” With carbs severely restricted and with protein only somewhat limited to avoid interfering with ketosis, the rest of a dieter’s calories will need to come from fat, though McDonald cautions against relying too heavily on macronutrient ratios. “I don’t care about the percentages — they tend to be misleading,” he says. “But in general, a properly set-up ketogenic fat-loss diet usually ends up being about 40–45% of calories from protein, maybe 50% fat and the rest carbs.” While some might think 50% of calories from fat looks dangerously high, McDonald points out that as long as your total calories are in check, you won’t be at risk. “In a caloric deficit fat content doesn’t really matter,” he says. “Some early studies found that blood lipid levels were horrible on high-saturated-fat ketogenic diets, but only when the subjects weren’t losing weight. On a cutting diet, fat intake really won’t matter much.”

Like any training or dieting method, the ketogenic experience can be as complex as you want it to be, and variations of the diet have evolved to suit different goals. McDonald explains: “Because ketosis is defined as the presence of ketones in the blood above a certain concentration, there’s definitely a cutoff point. But it’s possible to get into deeper levels depending on the degree of carbohydrate restriction. A diet containing exactly 100 grams of carbohydrate will probably just skirt ketosis, but a diet with zero carbohydrates is more likely to cause a deeper degree of ketosis and a higher level of ketones in the bloodstream.”

In addition to varying degrees of ketogenesis depending on net carb intake, there are also ways of manipulating carb timing to serve specific goals, resulting in standard, cyclical and targeted diets. “A standard ketogenic diet,” according to McDonald, “is simply low carbohydrate all the time. It’s most appropriate for inactive or obese folks, or for folks who only do low-intensity training.” But for bodybuilders and other athletes who endure grueling training sessions, this extreme low-carb approach will eventually deplete all muscle glycogen, meaning performance will suffer. “These folks have to find some way to add carbohydrates to their diet while remaining ketogenic,” McDonald says. Hence the development of cyclical and targeted versions of the diet.

“Cyclical ketogenic diets include periods of high-carbohydrate intake that can last from 1–3 days,” McDonald explains. “Done right, this carb surge can cause an anabolic rebound and even muscle growth as the dieter comes out of the low-carbohydrate phase.” But periodic bursts of carb intake aren’t always the answer. “Not everyone responds well to big carb loads,” he says. “Either they feel terrible or they end up regaining some fat. Enter the targeted ketogenic diet, which simply places carbs around training only. So on heavy weight-training days, a bodybuilder might consume 25 grams of carbs with some whey protein 30 minutes before their workout and another 25–50 grams with protein afterword. The rest of the day and any off-days would be kept low-carbohydrate. This way you get the benefits of being in ketosis while still being able to train intensely.”

The bottom line is that if you train hard, you’ll need to find a way to occasionally refeed carbs that doesn’t take you out of the ketogenic fat-burning zone and doesn’t leave you feeling fatigued. As for the type of carbs you should choose, McDonald claims it’s not an issue. “When carbs are that restricted, the source isn’t relevant,” he says. “But most will find that focusing on vegetables with small amounts of fruits, which refill liver glycogen, will help keep them full. A small amount of starches and grains will be fine, but with carbs set at 100 grams a day there isn’t much room for them.”


Knowing Whether You’re Ketogenic


So how do you know when you’ve reached ketogenesis? Many bodybuilders use a product called Ketostix, which are designed to change color when they come into contact with ketone-containing urine. But McDonald questions their reliability: “The defining characteristic of ketosis is blood concentration of ketones, which is harder to measure — and no, you can’t bleed on the Ketostix.” Ketogenic dieters do, however, notice that their urine takes on a peculiar smell, and many notice a metallic taste in their mouths, as excess ketones are often excreted through both urine and breathing.

Bodybuilders should also be aware that reaching ketosis isn’t always a smooth ride. If you’ve always relied purely on carbohydrate for energy, you’ll need to endure a transitional period while your body makes the switch. “It usually takes most folks about 2–3 weeks to fully adapt to ketosis,” McDonald says. “The brain is the main issue. It has to adapt to using ketones for fuel, and many people initially feel like they’ve been hit by a truck. But getting 3–5 grams of sodium, at least one gram of potassium and 300–500 milligrams of magnesium per day helps with fatigue in most people. Every so often, however, you find someone who just never seems to adapt to ketosis. If after three weeks they still feel terrible, they should pick another diet.”

Once you’re burning bodyfat in the form of ketones, you may also need to make some changes to your training. “Bodybuilders must keep some amount of heavy training in their schedule when they’re ketogenic,” McDonald insists. “If they use higher reps and lighter weights, they’ll risk losing muscle. They can do high-rep stuff in addition to heavy work, but they have to lift heavy.” You’ll likely also need to rethink your training volume. “Many find that their ability to use high volumes in the weight room suffers,” he says. “In those cases they should do a few heavy sets and then get the hell out of the gym.” And trainers who are used to using high-volume sets to burn extra calories can relax. “The diet will cause fat loss, and the training should be geared just toward maintaining muscle,” he explains.

One of the most common questions McDonald hears concerns cardio. After all, if the ketogenic diet is so adept at torching fat, is cardio really necessary? “So long as bodybuilders are in a caloric deficit,” he says, “they’ll lose fat without cardio as long as they continue weight training. But some low-intensity cardio can still be helpful. Some small-framed dieters can cut calories only so far, so cardio is the only way to create enough of a deficit for them to lose fat.”


Staying Ketogenic


If the ketogenic diet started as a medical treatment, and if following it works so reliably for nearly anyone who’s willing to endure a brief but rocky transition, why does it remain controversial? A lot of the concerns, according to McDonald, have to do with the lack of long-term studies on adult trainees. “Epileptic children have been kept on ketogenic diets for several years with no ill effects,” he explains, “but there simply isn’t any long-term data.” He adds that there’s no need for dieters to stay ketogenic for too long. “Bodybuilders using a ketogenic diet for cutting shouldn’t be doing it for several years unless their mass-gaining phase went very, very wrong,” he says.

The existing scientific literature on the ketogenic diet also raises questions about how effectively the brain functions on few carbs. “The brain can’t use fatty acids for fuel,” McDonald explains. “You’ll often hear that the brain can only use carbohydrate, to the tune of about 100–120 grams of carbs a day. But this assumption ignores ketones as a source of fuel. In fact, the body produces ketones to provide an alternate fuel for the brain during periods of total starvation. After about three weeks, the brain will actually derive about 75% of its total fuel requirements from ketones, and the body can manufacture its own glucose to fill in the rest.” Those emergency mechanisms aside, your brain will still function better with moderate carbohydrate intake, which is why trainers typically set the bar around 100 grams a day.

There’s also the question of ketoacidosis, a condition that can be fatal in extreme cases. “Ketoacidosis is a situation where the body produces an absurd amount of ketones, which cause a host of problems,” McDonald says. But he adds that this unchecked ketone production, which dangerously alters your blood pH levels, is rarely a problem for healthy dieters. “It’s something that Type 1 diabetics have to worry about, but practically speaking, it will never occur in a non–Type 1 diabetic dieter. The body has several control points that prevent ketoacidosis from ever showing up in typical dieters. It’s only an issue because many mainstream nutrition types constantly confuse ketosis with ketoacidosis,” he says.

Overall, there may be some merit to the concerns surrounding the ketogenic diet, particularly for individuals with pre-existing conditions like diabetes or for trainees whose bodies never make it through that three-week slump to start burning ketones efficiently. But for the average dieter who strictly maintains a minimum carb intake and who doesn’t stay in ketosis year round, the benefits of rapid fat loss and sustained muscle are very real. So whether you’re a bodybuilder with a stage-ready deadline or simply an avid lifter who’s in a hurry to show off your hard-earned muscle, ketoland can be a very good place to be.

For more of Lyle’s work on the ketogenic diet, visit his website at