The ketogenic diet, or "keto" for short, has gained significant popularity for its potential health benefits, including weight loss, increased energy, and stabilized blood sugar levels. But how does this diet, which drastically reduces carbohydrate intake in favor of fats, affect your ability to lift weights and build muscle? This article explores the relationship between the ketogenic diet and weightlifting, providing insights for those looking to combine these two practices.
Understanding the Keto Diet
The keto diet aims to shift the body into a state of ketosis, where it primarily burns fat for fuel instead of carbohydrates. When carbohydrate intake is severely restricted, the body breaks down stored fat into ketones, which then serve as an alternative energy source.
The Impact of Keto on Exercise Performance
While the keto diet may offer certain advantages, its effect on exercise, particularly high-intensity activities like weightlifting, is a subject of debate.
High-Intensity Exercise and Keto
High-intensity exercises rely heavily on carbohydrates for fuel. The body stores carbohydrates as muscle glycogen, which provides a readily available energy source for activities requiring short, intense bursts of energy. However, on a keto diet, the body's primary fuel source shifts to fat, which is not as efficiently burned as carbohydrates for high-intensity activities.
A small study from February 2017, involving 42 healthy adults on a six-week ketogenic diet, revealed a decline in endurance capacity and peak power. Andy Galpin, PhD, a professor of kinesiology at California State University, Fullerton, suggests that the keto diet might not be ideal for improving performance in activities requiring intense bursts of energy.
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Fat Burning and Steady-State Aerobic Exercise
Although keto may not be optimal for weightlifting, it can be effective for burning fat during steady-state aerobic exercises like distance running or cycling. A 2017 study involving elite race walkers demonstrated that those on a ketogenic diet significantly increased fat burning during training compared to those on a standard carbohydrate-inclusive diet. However, it's important to note that the keto group experienced greater exertion and were less likely to complete their assigned workouts.
The Adaptation Period
As the body adapts to ketosis, it becomes more efficient at using fat for energy. Initially, this adaptation process may lead to decreased energy levels during workouts. However, some research suggests that athletes can successfully increase their ability to use fat as fuel. A July 2017 study indicated that while athletes on a high-fat diet initially experienced reduced energy, their energy levels returned later on, especially during exercise.
Calorie Burning and Weight Loss
A 2018 study revealed that overweight adults who replaced carbohydrates with fat burned approximately 250 more calories per day than those on high-carbohydrate, low-fat diets. This difference in caloric burn can contribute to weight loss, as the body needs to burn more calories than it consumes.
Muscle Mass and Keto
The keto diet's impact on muscle mass is a crucial consideration for weightlifters.
Maintaining vs. Adding Muscle
If your goal is to maintain existing muscle mass, a ketogenic diet may be suitable. However, if you aim to build muscle, the lower calorie and protein intake often associated with keto can pose challenges. Building muscle on keto is possible but less efficient due to the reduced availability of carbohydrates, which the body stores in muscles and uses for muscle growth.
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Burning Fat vs. Losing Fat
While the keto diet can train your body to use fat as a fuel source, it doesn't automatically translate to fat loss. To lose fat and weight, you still need to burn more calories than you consume. When on keto, you burn more fat, but you also store more fat because a larger percentage of your calories come from fats.
Weightlifting on Keto: Optimizing Your Approach
Given the energy demands of intense weightlifting, a ketogenic lifestyle may not always align perfectly with a bodybuilding regimen. Carbohydrates provide fuel for muscles, which store them as glycogen for strength training sessions.
Macronutrient Balance
Andrea N suggests that weightlifters need five to seven grams of carbohydrates per kilogram of body weight. Men and women who lift weights multiple times a week need at least half of their calories from carbohydrate sources. It's important to choose these carbohydrates wisely, opting for nutrient-rich sources rather than processed foods.
Protein Intake
Adequate protein intake is crucial for muscle growth, repair, and recovery. Consuming around 20 grams of protein in high-protein meals, especially after workouts, is generally considered optimal for muscle growth.
Caloric Intake
Running a calorie deficit leads to weight loss but not muscle gain. To gain weight and build muscle, you need to consume more calories than you burn. Calculate your base metabolic rate (BMR) and the calories burned through daily activity and exercise to determine your caloric needs.
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Macro Ratios
The ratio of macronutrients (carbohydrates, protein, and fat) matters depending on your goals. To increase weight gained from fat, emphasize carbohydrates as well as fat, as fat is the most calorie-dense macronutrient.
Creatine
Creatine is a primary fuel source for the first 10 seconds of each set during weightlifting. Without sufficient energy, proper form may suffer.
Hydration
A keto diet can lead to poor performance by decreasing muscle fullness and hydration.
Building Muscle on Keto: A Practical Guide
Despite the challenges, it is possible to build muscle on the keto diet. Here's how:
Calorie Intake
To build muscle, consistently eat more calories than you burn. Determine your maintenance calories and increase your intake by 15%. Track your weight and adjust your calorie intake monthly to account for changes.
Protein Intake
Consume 0.7-0.9 grams of protein per pound of body weight (1.6-2.0 grams per kg) to support muscle growth. Studies have shown that people can safely consume around 1 gram of protein per pound of body weight (2.1 grams per kg) and stay in ketosis.
Carb Intake
Restrict your carb intake to fewer than 50 grams per day to maintain ketosis. Consider timing your carb intake around workouts to aid exercise performance.
Fat Intake
After accounting for protein and carbs, fat should make up the rest of your diet. Calculate your daily fat requirements based on your calorie, protein, and carb needs.
Resistance Training
Engage in resistance training at least twice a week to promote muscle growth. Incorporate exercises like squats, bench presses, pullups, and pushups into your routine.
Supplements
Consider using protein powder supplements to reach your daily protein needs. Creatine monohydrate can also aid gym performance and muscle gain. Ensure adequate intake of sodium, potassium, and magnesium through diet or supplements.
Additional Tips for Success
- Stay Patient: Allow your body time to adapt to ketosis.
- Track Carb Intake: Monitor your carb intake to stay within the 50-gram limit.
- Prepare for Side Effects: Be aware of potential side effects like the keto flu.
- Beware of Hidden Carbs: Check for hidden carbs in beverages and condiments.
- Test Ketone Levels Regularly: Use keto strips or a breath test to monitor your ketone levels.
- Get Plenty of Sleep: Prioritize proper sleep for muscle growth and exercise performance.
Scientific Evidence
Research suggests that ketogenic diets can be effective for reducing total body and fat mass, but they may also impair resistance training-induced muscle hypertrophy. Some studies have reported detrimental effects on muscle mass when KDs are combined with resistance exercise interventions.
- A study with Olympic-class weightlifters found that a 3-month ad libitum KD resulted in a total loss of body mass, with a significant portion attributed to muscle.
- A trial with bodybuilders following an 8-week energy-balanced KD found a significant reduction in total body and fat mass, while only the group on a westernized diet showed an increase in muscle mass.
- Two recent studies analyzing the effects of an 8-week KD in strength-trained men and women found that the KD resulted in a lower energy intake and reduced fat mass, but participants on the KD showed no changes in fat-free mass.
However, one randomized controlled trial reported superior hypertrophic effects in resistance-trained participants following a KD compared with a non-KD when reintroducing carbohydrates for one week.
Potential Mechanisms
Several mechanisms have been proposed to explain the potential detrimental effects of KD on muscle mass:
- KD-induced glycogen reductions may explain the loss of muscle mass due to the hydrophilic properties of glycogen granules.
- Low carbohydrate availability might attenuate resistance training-induced adaptations through a suppression of anabolic pathways.
- KD can lead to a reduction in insulin levels, which can stimulate muscle protein synthesis and reduce muscle protein breakdown.
- Preclinical evidence suggests that KD might promote AMP-activated protein kinase (AMPK) phosphorylation, which can inhibit anabolic pathways.