CLINICAL REVIEWS

By Bill Campbell, Ph.D., Exercise and Performance Nutrition Laboratory, University of South Florida

Burn Fat with Kettlebell Training?

"Adding kettlebell exercises into your workout routine can add variety to your program, give you a full-body workout, and burn those calories!"

Farrar RE, et al. Oxygen Cost of Kettlebell Swings. Journal of Strength & Conditioning Research 24(4): 1034-1036, 2010. Kettlebell training has become very popular in strength and conditioning routines, commercial fitness programs (such as Crossfit), and for thousands of fitness enthusiasts. It's touted as a viable way to increase muscular strength, muscular endurance, and cardiorespiratory fitness while reducing bodyfat. However, little to no research exists (at least in the English language) about the effectiveness of Kettlebell training in relation to caloric expenditure.

So researchers from Truman State University decided to investigate how many calories were expended during a popularly recommended kettlebell workout: Ten college-aged men completed a kettlebell exercise routine consisting of as many two-handed swings as could be completed in 12 minutes using a 16-kg kettlebell. Subjects completed an average of 265 swings during the 12 minutes (or an average work rate of 22 swings per minute).

Using sophisticated equipment (i.e., a device known as a metabolic cart) that is standard in most exercise physiology laboratories, it was reported that the males (who weighed 170 pounds on average) who participated in this study burned approximately 160 calories during the 12-minute kettlebell workout. Although females were not tested in this study, a 130-pound female would have expended about 120 calories. As a comparison, running at six miles per hour for 12 minutes would expend nearly the same amount of calories for males and females.

Hence, this study demonstrates that the caloric expenditure is equivalent to a moderate-intensity run. So adding kettlebell exercises into your workout routine can add variety to your program, give you a full-body workout, and burn those calories!

What Type of Protein Increases Metabolic Rate to the Greatest Extent?

Acheson KJ, et al. Protein Choices Targeting Thermogenesis and Metabolism. American Journal of Clinical Nutrition, 93: 525-534, 2011.

The thermic (heat) effect of food is defined as an increase in metabolic rate due to an increase in cellular activity associated with the digestion, absorption, and metabolism of food. The higher the thermic effect of a given food, the more calories burned in the hours following the ingestion of that food.

"If you already include whey protein as one of your sources of protein, you are likely aware of its superior ability to increase rates of protein synthesis."

Protein, as compared to carbohydrates and fats, increases energy expenditure to the greatest extent. In fact, the energy cost of digesting, absorbing, and metabolizing protein is 23%, as compared to only 6% for carbohydrates and 3% for fat. While it's clear that proteins have a greater thermic effect than do either carbohydrates or fats, little research has been conducted to determine the possible effects of different protein sources and their impact on metabolism.

Researchers from Switzerland provided three different meals (with each meal containing 459 calories) to participants. These meals provided 50% of the calories from protein, 40% of the calories from carbohydrate, and 10% of the calories from fat. The only difference between these three meals was the source of the protein—one meal contained only whey protein, another meal contained only casein protein, and the other protein-containing meal contained only soy protein.

After each participant ingested these meals, metabolic rate was measured over the next five and one-half hours to determine which source of protein elicited the greatest increase in metabolic rate.

The thermic effect of whey protein (inducing a 14.4% increase in metabolic rate) was significantly greater than that of either casein (which induced a 12% increase in metabolic rate) or soy (which induced an 11.6% increase in metabolic rate).

If you already include whey protein as one of your sources of protein, you are likely aware of its superior ability to increase rates of protein synthesis. The data from this study adds yet another benefit of ingesting whey protein—its ability to maximize metabolic rate. Over time, this characteristic may induce favorable changes in body composition.

High-Intensity Interval Training vs. Traditional, Low-Intensity Bouts of Exercise

Macpherson RE, et al. Run Sprint Interval Training Improves Aerobic Performance but Not Maximal Cardiac Output. Medicine & Science in Sports & Exercise 43(1):115-122, 2011.

High intensity interval training (HIIT) has been growing in popularity over the past decade with many experts proclaiming it's the most effective way to burn fat. It generally refers to repeated sessions of relatively brief, intermittent exercise, often performed with an ''all-out'' effort, and is normally associated with cycling or running. Typically, a single maximal effort lasts only a few seconds with multiple efforts separated by up to a few minutes of rest or low-intensity exercise.

"The total amount of time spent exercising over the six-week study was approximately 13 hours for the endurance training group and only 45 minutes for the high-intensity running group!"

In contrast to HIT, traditional running or cycling involves constant speeds (such as running at seven miles per hour for 30 minutes or cycling at 18 to 24 miles per hour for 60 minutes).

Which one of these approaches is better in terms of favorably altering body composition and exercise performance?

Well, a recent investigation studied the effects of HIIT training (sprinting) and traditional running in young, physically active subjects. The high-intensity group performed 30-second all-out sprints on a treadmill four to six times per session with four minutes of recovery between each bout. The endurance training group performed low-intensity running (65% VO2max) on a treadmill for 30 to 60 minutes. Each group trained three times per week for six weeks.

At the end of the six-week study, it was reported that both groups lost a significant amount of bodyfat. Specifically, the HIIT group lost almost four pounds of fat, and the endurance training group lost almost two pounds of fat. In addition, both groups improved their time while running 2,000 meters with the HIIT group improving their running time by 4.6% and the endurance training group improving their time by 5.9%.

One could easily conclude both types of programs are effective for improving body composition and exercise performance. While this is true, the authors of this study stated: "Despite a fraction of the time commitment, HIIT induces similar body composition and performance adaptations as traditional endurance training."

In fact, the total amount of time spent exercising over the six-week study was approximately 13 hours for the endurance training group and only 45 minutes for the high-intensity running group! Talk about getting the most bang for your buck (or time in this instance!). This is a significant difference in the actual amount of time spent exercising.

One caveat… it must be noted that some individuals do not tolerate high-intensity training very well. For these types of individuals, a lower-intensity exercise program is equally effective but requires a greater time commitment.

Boost Your Weight Loss with Meal Replacements

"There are several great-tasting products on the market that make the cumbersome process of losing weight more manageable."

König D, et al. Effect of meal replacement on metabolic risk factors in overweight and obese subjects. Annals of Nutrition & Metabolism 52(1):74-78, 2008.

Protein-based meal replacement products are commonly used as part of a healthy weight-loss program. Often, these products are commercially available as meal-replacement shakes and meal-replacement bars and are relatively high in protein.

To test the effectiveness of a protein-based meal-replacement shake, researchers assessed weight loss, fat loss, and waist reduction in overweight men and women over a period of six weeks.

Subjects were divided into two groups: a fat-restricted low-calorie diet group and a low-calorie meal-replacement diet group. The low-calorie diet provided approximately 1,350 calories per day for women and 1,650 calories per day for men. The meal-replacement group dieters were instructed to replace two of their three daily meals with a soy-yogurt preparation. This diet provided about 1,000 calories per day for women and 1,200 calories per day for men.

After six weeks, the low-calorie diet induced nearly a seven-pound reduction in bodyweight while the meal-replacement diet induced a 14-pound reduction in body weight. Fat loss in the low-calorie diet and meal-replacement diet was six pounds and 11 pounds, respectively. Waist reduction was nearly two centimeters in the low-calorie diet group and was six centimeters in the meal-replacement group.

In each of these measures, the meal-replacement group realized statistically significant improvements as compared to the low-calorie group.

Though the low-calorie diet group ingested a mean caloric intake of 1.5 times that of the meal-replacement group, the weight reduction in the meal-replacement group was 1.8 times higher.

If you are trying to lose weight, you may want to try a meal-replacement product. There are several great-tasting products on the market that make the cumbersome process of losing weight more manageable.

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