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Low-Carb Diet & Weight Lifting

author image Andrea Cespedes
Andrea Cespedes is a professionally trained chef who has focused studies in nutrition. With more than 20 years of experience in the fitness industry, she coaches cycling and running and teaches Pilates and yoga. She is an American Council on Exercise-certified personal trainer, RYT-200 and has degrees from Princeton and Columbia University.
Low-Carb Diet & Weight Lifting
Weight-lifting programs benefit from moderate-carb diets. Photo Credit funduck/iStock/Getty Images

As a weight lifter, you might be tempted to try a low-carb diet to lose excess body fat and show off cut muscles. Carbohydrates are a primary macronutrient that provide energy and contribute to metabolic activities that stimulate muscle growth. Cutting back drastically on carbs can have dramatic effects on your performance in the gym, at least in the short term. Research isn't conclusive on whether a low-carb diet will help or hurt your weight lifting, so you might have to experiment on your own body to determine how low-carb eating affects you.

Potential Positives of a Low-Carb Diet

A low-carb diet does have some benefits, including stabilized blood sugar levels and possible weight loss. Although some very restrictive low-carb diets direct you to consume not more than 20 to 50 grams of carbs per day, the limitations of a moderate low-carb plan range from 100 to 150 grams per day. Compared to the standard American diet that includes 200 to 300-plus carbs daily, this is a notable reduction.

A weight lifter might be tempted to go low-carb to "lean out" and show off vascular muscles. Reducing your carb intake can reduce your overall calorie intake and cause you to lose water weight and bloating. When you cut out junk carbs, such as white bread, sweets and soda, you may also improve your overall nutrient profile.

Low-Carb and Weight-Lifting Performance

Research isn't conclusive on the effects of a low-carb diet on weight-lifting performance. A study published in the Journal of Strength and Conditioning Research in 2013 showed no effect on strength or power production in athletes who restricted carb intake from 40 percent of daily calories to 5 percent of daily calories for one week. That's equivalent to a person on a 2,000-calorie diet dropping from 200 grams of carbs per day to 25 grams per day.

An earlier study, published in Obesity in 2012, also found that participants on a calorie- and carb-restricted diet -- with about 16 grams of carbs per day -- lost more weight and experienced no reduction in strength after eight weeks, compared to participants on a restricted calorie, high carbohydrate diet of about 185 grams per day. Although this study was relatively small and did not involve athletes, it suggests that adaptation to a very low-carb diet does not negatively affect strength.

Fuel for Weight Lifting on Low-Carb Diets

Carbohydrates do convert into the glycogen stored in your muscles that your body uses for fuel when performing heavy lifts. With a moderate-carb diet of 100 to 150 grams daily, you may still get enough of these carbs to support your workouts. But, if cutting back to this moderately low level of carbs represents a dramatic shift in intake for you, consider gradually reducing your carb intake over the course of several weeks to prevent extreme fatigue and weakness.

On strict low-carb diets of 50 or fewer grams daily, your system for fueling shifts. Your body becomes efficient at burning fat and produces ketones, which are chemicals your body uses in lieu of glycogen. When you make the transition to this new fuel system, you may feel fatigued and performance may suffer. After a few weeks, however, you become "keto-adapted" and feel energized. Researchers in Obesity's 2012 study surmise that such adaptation explains the participants' maintenance of strength.

Not all research supports a low-carb or very restrictive low-carb diet for weight lifting. A 2004 study published in Nutrition and Metabolism studied cultures that traditionally follow a diet very low in carbohydrates. The researchers found that adaptation happens in these cultures and won't compromise regular physical labor or recreational activity, but isn't appropriate for competitive weight lifters or athletes.

A Balanced Low-Carb Plan

Regardless of whether a weight lifter follows a low-carb eating plan, he needs ample protein to support muscle repair and recovery. Aim for 0.75 to 1.0 grams of protein per pound of body weight as a strength-focused athlete. Maintain this level of protein consumption even if you shift to a low-carb plan.

An effective low-carb diet relies on fat to make up for calories missing through carb restriction. A high-fat diet helps shift you into the state of ketosis that provides you with the alternative sources of energy and fat loss that you're after. Coconut oil, olive oil, scant servings of nuts and avocado and fatty cuts of meat and fish are excellent fat sources.

Ultimately, you have to determine the carb level appropriate for you and your performance goals. No current evidence exists that a low-carb diet improves weight-lifting performance or results, but it may not hamper them either. Monitor your level of fatigue and strength while on a low-carb plan. If you feel weak or tired as the weeks progress, you may need a slightly higher carb intake to support your activity level.

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