By Dr. Mercola
When scientists at the University of Florida realized their student athletes needed a quick source of energy and hydration, the carbohydrate-loaded sports drink Gatorade was born.
In the 40 or so years since then, a boatload of carbed-up diet plans and so-called performance-boosting drinks and foods have hit the market, all espousing the benefits of carbohydrates and the concept of carbohydrate-loading. The idea is to saturate yourself with carbs so your muscles will have plenty of glycogen to go on while you exercise.
This worked fine for really fit athletes that were intensely working out and sweating copiously, as they needed to replace those fluids and carbs. However, it is totally inappropriate to transfer this to the vast majority of non-athletes that exercise casually, or just to get healthy, in which they are typically losing large amounts of sweat or burning carbs during their workout.
In fact new research shows there's more to it than just stuffing yourself with carbs. Proteins, glutamic acid, leucine, and other essential amino acids also play a part in energy and sports nutrition―and there's a certain timing of consumption that goes with them to assure that you're getting the best results for your efforts.
The featured article in Functional Ingredients discusses the use of carbohydrates, protein and amino acids, caffeine, beta-alanine and creatine in sports nutrition.
While I agree on many points, such as the importance of whey for stimulating muscle protein synthesis, I strongly disagree with the article's stance on using multiple types of sugars to replenish glycogen stores. As I'll discuss below, the focus on carbs is one of the most detrimental pieces of advice that is still widely promoted to athletes and non-athletes alike.
Additionally, the article does not review the exciting new research on the potential benefits of intermittent fasting to boost exercise benefits, which I will expound upon below. This is an oft-ignored factor that can have a potent impact, although it's not necessarily recommended for everyone, or for every circumstance.
Sports Nutrition—Going Beyond Carb-Loading
The food you eat has an immense impact not only on your general health, but on the benefits you will ultimately reap from your workouts. What you eat can either add to or detract from your exercise benefits, and if you're devoting the time to exercise, you'd be well advised to harness your meals to support your goals, not detract from them.
First and foremost, contrary to popular advice, to maximize the benefits of exercise, you'll want to avoid fructose and other sugars unless you are engaged in intensive and prolonged cardio exercises that will allow you to burn these sugars, especially fructose, and not store them as fat.
This means that most casual exercisers and those seeking to improve body composition and optimize health and fitness rather than boost athletic performance or competitiveness, need to ditch the energy drinks, sports drinks, most energy bars and even "healthy" drinks like vitamin water, as these will effectively sabotage your exercise benefits. Fructose, which is found primarily in the form of high fructose corn syrup, is particularly detrimental as it tricks your body into gaining weight by turning off your body's appetite-control system.
This happens because fructose does not appropriately stimulate insulin, which in turn does not suppress ghrelin (the "hunger hormone") and doesn't stimulate leptin (the "satiety hormone"). The end result is that you end up eating more causing uncontrolled accumulation of sugar metabolites in your liver, which then leads to insulin resistance. Fructose also rapidly leads to decreased HDL ("good" cholesterol), increased LDL ("bad" cholesterol), elevated triglycerides, elevated blood sugar, and high blood pressure—i.e. classic metabolic syndrome. And if that's not bad enough, fructose has shown to increase the levels of TNF-α, a pro-inflammatory cytokine known to inhibit fat burning and promote muscle wasting.
Exercise, which in and of itself improves insulin sensitivity will NOT compensate for excessive use of fructose.
Now, in terms of its impact on your fitness, it's important to realize that consuming fructose, including that from processed fruit juices, within two hours of your workout (before or after) will also decimate your natural human growth hormone (HGH) production.
Increasing your HGH level is a major benefit of exercise, provided you're using high-intensity interval training, which is the primary way to boost HGH naturally (you can also use super-slow weight training to accomplish similar results). HGH is also known as "the fitness hormone," and some athletes pay a lot of money for HGH injections. There are significant drawbacks to doing that, and the combination of eliminating fructose and using high-intensity interval training while fasting is definitely the preferred way to optimize your HGH.
Three Factors of Effective Fitness Nutrition
Fitness expert Ori Hofmekler, author of Maximum Muscle Minimum Fat, and Unlock Your Muscle Gene, was responsible for first enlightening me to the curious paradox of boosting muscle building by exercising while fasted (meaning on an empty stomach). As it turns out, amino acids and protein serve not just as building blocks for tissues and muscle. Certain amino acids can also signal genes in your muscle to grow and to build protein, and they do that even during times of food deprivation as long as these amino acids are circulating through your blood stream.
Moreover, scientists have found that the ratio between protein and carbohydrates is critically important, especially as you age. Many make the mistake of eating too many carbs in relation to protein and fat. Research shows that high-carbohydrate diets fail to build muscle, even in younger people due to their detrimental effect on insulin. Again and again, it's the high-protein/high-fat/low-carbohydrate diet that proves the most effective both for muscle building and weight loss.
To summarize, there are three primary factors involved in effective fitness nutrition, to which you can then add the strategy of exercising while in a fasted state to further boost results:
- A high-protein, low-carbohydrate diet. Keep in mind that most people need between 50-70 percent healthy fats in their diet, which take the place of the carbs you're eliminating. In order to build muscle, you clearly need calories, but there's compelling evidence showing that calories from fat are far better than calories from carbohydrates
- Certain amino acids, the most notable of which is leucine (others can also be useful. Beta-alanine/carnosine, for example, has been found to improve performance in high intensity exercise and can help reduce muscle soreness). But remember that it is crucial that you avoid amino acid supplements of leucine. It is far better to get it from whole foods. Note that as free form amino acids, leucine has shown to disrupt insulin activity and cause insulin resistance. The highest source of leucine is high quality whey protein that is minimally processed and not whey protein isolate, which is overproccessed, and typically yields a massive distortion of protein and a loss of nutritional co-factors.
- Whether you choose to exercise on an empty stomach or not, your post exercise meal is crucial to stop the catabolic process in your muscle and shift the process toward repair and growth.
If you fail to feed your muscle at the right time after exercise, the catabolic process will go too far and can potentially damage your muscle. The correct time to eat is within 30 minutes after your workout. Your meal should include fast-assimilating proteins, such as high-quality whey protein with no sugar added. To learn more, please see this previous article that discusses the use of whey protein for optimal muscle building
If you cannot exercise in a fasted state due to fatigue, or simply opt not to for some other reason, you can also consume whey protein before exercise. It's an excellent breakfast choice. A 2010 study published in the journal Medicine and Science in Sports & Exercisei demonstrated that consuming whey protein (20g protein / serving) 30 minutes before resistance training can boost your body's metabolism for as much as 24 hours after your workout. It appears as though the amino acids found in high-quality whey protein activate certain cellular mechanisms (mTORC-1), which in turn promote muscle protein synthesis, boost thyroid, and also protect against declining testosterone levels after exercise.
In practical terms, consuming 20 grams of net protein from quality whey before exercise and another serving of 20-30 g net protein afterward will most likely yield the double benefit of increasing both fat burning and muscle build-up at the same time. Again, not everyone will need to eat something prior to exercise, but if you do, a high-quality whey protein is your best bet. It'll curb your hunger while still optimizing fat burning.
The only exception is if you are doing strength training, as when you are fasting for 14-18 hours you typically deplete most of you glycogen stores so it is difficult to lift your maximum weight to failure. Hence, if you are doing heavy lifting to failure, you may want to avoid training while fasting on those days. In these cases it is likely helpful to consume some healthy slow releasing starchy carbs the night before working out so your glycogen stores won't be depleted in the morning. Then, have whey protein as a pre-exercise meal to grant sufficient supply of branched chain amino acids for optimum muscle fueling during your workout.
Boost Fitness Results with Intermittent Fasting
Exercising on an empty stomach has been shown to have a number of health and fitness benefits. It may even be a key to keep your body biologically young. This is most easily accomplished if you exercise first thing in the morning, before breakfast. Part of the explanation for why exercising while fasted is beneficial is that this regimen complements your sympathetic nervous system (SNS) along with your capacity to burn fat. Your body's fat burning processes are controlled by your SNS, and your SNS is activated by exercise, and by lack of food.
The combination of fasting and exercising maximizes the impact of cellular factors and catalysts (cyclic AMP and AMP Kinases), which force the breakdown of fat and glycogen for energy. This is why training on an empty stomach will effectively force your body to burn fat.
Regardless of when you choose to exercise, remember that you need to eat 30 minutes after your workout, which will effectively break your fast. If you exercise in the late morning or early afternoon, you could break your fast by including 20 grams net protein from a fast-assimilating source like a high-quality whey protein concentrate 30 minutes before you start your exercise, and then have another recovery meal 30 minutes after.
Exercise and fasting yield acute oxidative stress, which keeps your muscles' mitochondria, neuro-motors and fibers intact. You may have heard of oxidative stress before in a negative light, and indeed, when it is chronic it can indeed lead to disease. But acute oxidative stress, such as occurs due to short intense exercise or periodic fasting, actually benefits your muscle.
As explained by Ori Hofmekler:
". . . it's essential for keeping your muscle machinery tuned. Technically, acute oxidative stress makes your muscle increasingly resilient to oxidative stress; it stimulates glutathione and SOD production in your mitochondria along with increased muscular capacity to utilize energy, generate force and resist fatigue. Hence, exercise and fasting help counteract all the main determinants of muscle aging. But there is something else about exercise and fasting. When combined, they trigger a mechanism that recycles and rejuvenates your brain and muscle tissues.
Growing evidence indicates that fasting and exercise trigger genes and growth factors, which recycle and rejuvenate your brain and muscle tissues. These growth factors include brain derived neurotropic factor (BDNF), Insulin Like Growth Factor (IGF-1), and muscle regulatory factors (MRFs); they signal brain stem cells and muscle satellite cells to convert into new neurons and new muscle cells respectively. Incredibly, BDNF also expresses itself in the neuro-muscular system where it protects neuro-motors from degradation. This means that exercise while fasting signals your body to keep your brain, neuro-motors and muscle fibers biologically young."
Amino Acids—Essential Building Blocks to Strengthen Muscles
As mentioned earlier, the amino acid leucine is one of the most important for fitness. It's part of branched-chain amino acid found in certain foods, and serves multiple functions in your body, one of which is signaling the mTOR (Mammalian Target of Rapamycin) mechanism, which signals protein to be created and builds your muscle. But that's not all.
Ori Hofmekler explains:
"Leucine has shown to promote the anti-inflammatory cytokine interleukin 15 (IL-15), which has been regarded as the most powerful fitness promoting protein produced by your muscle. IL-15 acts as an anti-inflammatory, anti-obesity, muscle-regenerating signaling agent with unmatching effects on body transformation and anti-aging.
Furthermore leucine along with calcium blocks the obesity promoting effect of excess Vitamin D calciferol in adipose tissues (excess of vitamin d in fat cells induces central obesity which can be blocked by calcium/leucine intake such as from dairy, particularly whey protein). Finally, leucine/IL 15 anti-inflammatory actions have been linked to mitochondrial biogenesis, increased thermogensis, and increased energy utilization efficiency probably via activation of the longevity gene SIRT-1."
Leucine also indirectly promotes the increase of glutathione in your body, as its anti-inflammatory actions can help spare glutathione molecules that would have otherwise be recruited to counteract inflammatory processes.
However, in order to be effective, you need far more than the recommended daily allowance (RDA) of leucine. The reason for this is because even though leucine is relatively abundant in our food supply, it does not appear in high concentrations, and is often wasted as an energy substrate or used as a building block rather than an anabolic agent. This means that to establish the right anabolic environment, you need to increase leucine consumption beyond maintenance requirements.
That said, keep in mind that using leucine as a free form amino acid can be highly counterproductive as when free form amino acids are artificially administrated, they rapidly enter your circulation while disrupting insulin function, and impairing your body's glycemic control. Food based leucine is really the ideal form that can benefit your muscles without side effects. The highest concentrations of leucine and other branched chain amino acids (BCAA) are found in dairy products; particularly whey protein. and quality cheese.
Based on nitrogen-balance measurements, the requirement for leucine to maintain body protein is 1-3 grams daily. To optimize its anabolic pathway, you need an estimated 8g - 16g of leucine daily. The following chart presents leucine content in common foods. As you can see, whey protein is ideal for getting sufficient amounts of leucine in your diet. You only need three ounces of whey protein, compared to a pound and a half of chicken to get 8 grams of leucine:
Leucine Content in food / per 100g
|Whey Protein Concentrate
|Raw Cheddar Cheese
What's Your Goal? Fitness or Longevity?
In closing, I want to share some additional insights from Ori Hofmekler with regards to intermittent fasting. It's important to realize that when it comes to diet and exercise, you actually have to tailor them to your end goal—either maximum fitness, or maximum longevity. You cannot accomplish both at the same time... This is even more pronounced for women, who also trade extreme fitness for their reproductive capacity. Below, Ori expounds on these issues.
By Ori Hofmekler
Gender is certainly an important factor in human and animal studies. Female-specific responses to fasting raise an interesting scientific phenomenon. Researchers have been finding evidence that there is indeed a tradeoff between virility and longevity of organisms. Apparently the same genes that promote human longevity may trigger biological mechanisms that suppress female reproductive capacity. Hence, fasting and intense exercise protocols, known to promote longevity, also lower estrogen level and thereby modulate body composition and suppress female reproductive capacity.
This is apparently part of an early adaption mechanism to primordial conditions of food scarcity and hardship, which requires increased strength and durability on the account of reproductivity. Hence, hard conditions are not biologically suitable times for pregnancy and child bearing.
I discussed this issue with Dr. Marc Mattson, Prof. of Neurosciences at Johns Hopkins University a few years ago. According to Mattson, women who fast or are on calorie restriction, have the tendency to get leaner, become increasingly addicted to physical exercise, and lose their menstrual cycle. Nonetheless, they seem to gain substantial improvements in all main biological markers of longevity – i.e. increased insulin sensitivity, increased GH secretion, improved lipid profile, improved anti-inflammatory cytokine profile, improved cognitive function, etc.
Note that fasting triggers the longevity gene SIRT-1, which regulates mitochondrial energy production along with the gene transcription promoter protein PGC-1α, which increases mitochondrial biogenesis and density in the muscle.
Yes, mitochondrial energy utilization efficiency is a key to longevity.
One of the most notable benefits of fasting is its profound anti-inflammatory effect. Fasting increases production of anti-inflammatory cytokines while suppressing pro-inflammatory cytokines such as TNF-α and IL-6. Note that pro-inflammatory cytokines produced by fat cells (adipokines) are associated with insulin resistance, obesity, metabolic syndrome, and a shorter life span; whereas anti-inflammatory cytokines, such as adiponectin and IL-15, are associated with improved insulin sensitivity, increased thermogenesis, decreased fat storage, increased muscle regeneration and increased life span (this probably deserves another article).
Finally, in view of the current epidemic of excess estrogen in females and males, caused by estrogenic chemicals and foods (such as petrochemicals and soy), fasting and IF can be used as an effective therapeutic strategy to balance estrogen and prevent related metabolic disorders and cancer.
To sum this up, the female-specific response to fasting or intermittent fasting is no different than the female response to intense exercise. There is indeed a tradeoff between benefits and side effects. And the question "should women fast" raises the same issues as the question "should women exercise intensely".