To fuel exercise, your body uses stored fat and carbohydrates in the form of muscle glycogen. As exercise intensity increases, greater amounts of fat and carbs are oxidized. But the rate of fat oxidation decreases after your reach about 70% of exercise capacity, accelerating the use of glycogen.

A study published in the European Journal of Sport Science examines whether L-carnitine influences this tradeoff. Because of carnitine’s role in transporting fat, researchers theorized that a reduction in muscle free carnitine might be one of the mechanisms behind the switch from fat to carbohydrate energy.

True Strength Moment: Muscle carnitine content can be increased by eating foods like lamb, fish, chicken, asparagus and dairy products. Supplementation can also increase carnitine, which might be important since there seems to be a correlation between carnitine availability and fat oxidation during high-intensity submaximal exercise.

Swimsuit season is right around the corner, and if you’ve been putting off planning out an effective diet and fitness strategy for weight loss, a study published in the Annals of Behavioral Medicine suggests tackling diet improvements and regular exercise at the same time produces optimal results.

Researchers recruited 200 adults aged 45 and older who hadn’t been eating very healthy or getting much exercise. Some were encouraged to start eating healthier and exercising right away while others focused on either diet or exercise for a couple of months before incorporating the other aspect into their weight loss program. Those who went all in with both diet and fitness were much more likely to get the recommended amount of exercise each week and consume 5 to 9 servings of fruits and vegetables daily.

True Strength Moment: While you probably aren’t eating as poorly as these middle aged subjects and are likely to be a lot more active than they were before this intervention, it might help to know that the second best option for weight loss was hitting the gym right away and dialing in your diet a little later. Now that you’re regularly hitting personal bests, take a look at how you’re reinforcing those gains in the kitchen.

Now that you’ve successfully cut down to size for swimsuit season, what’s the best diet strategy for keeping the weight off? Since 95% of people who successfully lose weight gain it back within a year, that’s a very important consideration. A study published in the journal PloS One suggests following a very low-carb diet instead of a low-fat program.

Boston Children’s Hospital put a group of obese young adults on a low-carb diet to lose weight. After reducing body weight by 10% to 15%, some continued a reduced carbohydrate eating strategy while others switched to a low-fat/low GI diet. Although rates of energy expenditure were similar following a meal, it remained lower for a longer amount of time with the low fat/low GI diet.

True Strength Moment: Successful weight loss has a way of increasing appetite while reducing metabolic rate. Adhering to a very low carbohydrate eating strategy can help you beat the odds. Try elevating carbohydrate consumption one day each week to restore glycogen reserves. This tactic might also stoke your metabolism for a short period of time.

L-carnitine has been used as a nutritional supplement for more than two decades.¹ It’s a trimthylated amino acid found primarily in animal proteins, with red meat regarded as the richest source, although humans are also capable of synthesizing L-carnitine from dietary amino acids. Its main function in the body is to aid in the metabolism of food into energy, but it also has been shown to be a valuable supplement for athletes by assisting the recovery process through the improvement of muscle tissue repair and reduction of muscle tissue damage.^2,3,4 What’s more, one study on healthy trained men showed that L-carnitine supplementation can significantly increase testosterone receptor concentration.⁵

Improves Recovery

Studies have shown that L-carnitine is a powerful ingredient that can help aid the post-workout recovery process. It acts as an antioxidant that can reduce free-radical formation, minimize muscle tissue disruption and promote recovery.^2,3,4 L-carnitine has even been shown to reduce muscle soreness after a workout.⁴ In the long run, proper recuperation is important for overall growth and development.

Testosterone Receptor Booster

Another important effect of L-carnitine is its ability to significantly increase testosterone receptor concentration. In fact, in one study, L-carnitine was shown to significantly increase testosterone (androgen) receptor concentration after only 21 days of supplementation in resistance-trained men.⁵ The increase in receptor availability is believed to lead to greater potential of free-testosterone utilization at the muscle fiber level. Free testosterone is the most usable form of testosterone available for pure, unadulterated growth and development of muscle.

References:

¹ Kelly, G., 1998. Alternative Medicine Review. 3(5):345-360.
² Kraemer et al., 2003. Journal of Strength & Conditioning Research. 17(3):455-462.
³ Volek et al., 2002. American Journal of Physiology – Endocrinology and Metabolism. 282:E474-E482.
⁴ Ho et al., 2010. Metabolism. 59:1190-1199.
⁵ Kraemer et al., 2006. Medicine & Science in Sport & Exercise. 38(7):1288-1296.
⁶ Swart et al., 1997. Nutrition Research. 17(3):405-414.
⁷ Wall et al., 2011. Journal of Physiology. 589(4):963-73.