The following article features a discussion between Susan Harmony Ph.D and myself. Susan sent me an e-mail informing me that I had misrepresented the science concerning exercise and saturated fat. Excerpts from our first debate were featured in last week’s newsletter. In this article I present our second debate. Susan’s comments appear in bold between the quotation marks.”You obviously have much to learn.” If you read my work I think you will find I have learned quiet a bit. Although I would agree I still have much to learn. As long as my brain is functioning I will attempt to keep on learning. Learning should be a life long process. Once an individual admits they have much to learn this process can continue. If a person assumes they have learned enough then learning usually comes to a stop.
“To remove bodyfat you need to use it as fuel. The muscle fibers that are fuelled by fat (‘slow twitch’ fibers ) are the ones that produce GENTLE movements” You don’t have to learn how to use fuel. Are you aware that you are burning fuel 24 hours per day? When you are sitting doing absolutely nothing you are burning fuel. Many tissues can use free fatty acids for fuel not just slow twitch muscle fibers. Losing bodyfat relies on way more than activity of the slow twitch muscle fibers (how about cal deficit). Do you realize to use slow twitch muscle fibers nervous stimulation is required (CNS requires cals although not fat calories)? High intensity exercise often results in a lower RQ (indicating higher proportion of fat) than low intensity exercise post-workout. Below is a brief description of what occurs during mobilization of stored fat and oxidation of fatty acids: The following is an excerpt from Fat Burning How it Works by Jamie Hale. I added a few additional comments to make the information more precise.
– Bodies 2 major stores of fat that provide energy 1) adipose tissue 2) intramuscular triglyceride (IMTG)
– Adipose tissue stores fat in the form of triglyceride (triacylglycerols). TG is composed of a glycerol backbone with three FFA attached to it.
– IMTG are droplets of fat stored within the muscle fiber.
– IMTG are contained within the muscle and can be used directly, FFA from adipose tissue must be carried through the bloodstream to the muscles to be used for energy.
– Fats are broken down to fatty acids and glycerol. Glycerol enters the glycolytic/glucogenic pathway via glyceraldehyde 3 phosphate (can be used to from TAG in liver as well). The free fatty acids move through the cell membrane of adipocyte, and bind to albumin in plasma. They are then transported to tissue where they enter cells. Keep in mind regardless of FFA blood levels the brain (although the brain can use ketone bodies) and erythocytes cannot use free fatty acids for energy. Breakdown of TG is initiated by HSL (hormone sensitive lipase), which is primarily influenced by insulin, and the catecholamines. HSL removes a fatty acid from carbon 1 and or 3 of TAG. Additional lipases including Diacyclglycerol and Monoacylglycerol remove the remaining fatty acids (Harvey & Champe 2005).
Adrenaline and nor adrenaline bind to beta-adrenergic receptors in fat cells stimulating HSL causing FFA release
FFA is burned in the mitochondria to produce ATP and acetyl-CoA”
Below I have provided further educational material.
The following is an excerpt from Knowledge and Nonsense: Ch. 5 Exercise: Fact or Fiction:
The best exercise for fat loss is low intensity, long duration aerobics
Dietary factors excluded the proportional use of fat during exercise is related to training intensity. The lower the intensity, the greater the proportion of stored fat burned. The higher the intensity, the greater proportional use of glycogen and/or the phosphagen system. The real question should be what type of exercise promotes chronic fat burning? The actual time spent training takes up a small portion of an entire day. Even if you trained two hours per day every day that still means you have twenty-two hours per day where you are not training. In this section, I will present the reader with scientific data that looks at fat oxidation during training, post-training, over a 24-hour time span, and long term. Dietary factors will not be addressed in this section because that is a different topic. Keep in mind, any training regimen must be supported with a proper nutritional protocol that matches training objectives.
As you’re sitting there reading this, you are burning proportionally more fat than you would be sprinting 100 meters (you’re relying primarily on the phosphagen system). Does that surprise you? It is commonsense that sprinting 100 meters would be more beneficial than reading for net fat loss. The key word is net fat loss. Net fat loss depends on more than proportional fat oxidation while training. Don’t forget the total calories burned during training. Also, consider the absolute fat oxidation during training. Often, an exercise may burn a higher amount of proportional fat, but due to the low calorie expenditure when compared to a higher intensity exercise (up to 75–80 percent), the absolute amount of fat oxidation may actually be lower. Higher intensity activity also generates a more significant effect on excessive post-exercise oxygen consumption (EPOC).
Calories burned while exercising
Most trainees overestimate the significance of caloric expenditure while training. The amount of calories burned while training is generally very low relative to total calorie consumption. During low intensity exercise, approximately 5 kcals per minute are oxidized while increasing intensity could result in burning up to 10 kcals per minute.
In general, weight training results in a caloric expenditure of about 7–9 calories per minute including rest periods. Significant gains in skeletal muscle tissue can result in higher calorie expenditure over time.
Fat oxidation: During and immediately following exercise
Fat oxidation during exercise tends to be higher in low intensity treatments, but post-exercise fat oxidation tends to be higher in high intensity treatments. Phelain’s (1997) team compared fat oxidation at three hours post-exercise of 75 percent VO2 max versus the same calories burned at 50 percent. Fat oxidation was insignificantly higher during exercise for the 50 percent group but was significantly higher for the 75 percent group three hours post-exercise. Lee’s (1999) team compared, in college males, the thermogenic and lipolytic effects of exercise pre-fueled with milk + glucose on high versus low intensity training. Pre-exercise intake of the milk/glucose solution increased excess post-exercise oxygen consumption significantly more than the fasted control group in both cases. The high intensity treatment had more fat oxidation during the recovery period than the low intensity treatment.
Fat oxidation: The 24-hour effect
Melanson’s research team (2002) carried out a study that compared an even mix of lean, healthy men and women aged 20–45 with identical caloric expenditures at a 40 percent VO2 max training intensity to a 70 percent VO2 max intensity. There was no difference in net fat oxidation between the low and high intensity groups at the 24-hour mark.
Saris & Schrauwen (2004) conducted a study on obese males using a high intensity interval protocol versus a low intensity linear one. There was no difference in fat oxidation between the high and low intensity treatments at 24 hours. In addition, the high intensity group actually maintained a lower respiratory quotient (burned higher proportion of fat) post-exercise.
Fat oxidation: Long term/chronic effects
Long-term tests are the most important when looking at total fat loss. A common finding with long-term testing is that when caloric expenditure is the same during training between high and low intensity exercise minimal differences are seen in fat loss. Another significant finding generally found is that high intensity training usually results in maintenance or growth of muscle tissue. Low intensity training usually results in loss of muscle tissue.
The majority of research indicates that high intensity interval training (interval training alternates periods of short near maximal intensity activity with low to moderate intensity activity) is superior for both fat loss and lean mass gain/maintenance. Tremblay’s team (1994) did a study comparing HITT versus steady state endurance training on young adults over a 20-week period. The HITT used a progressive program working up to five, 90-second intervals near their max heart rate thee times per week. The steady state endurance group worked up to 45 minutes of exercise five times per week. Although the interval training group only worked out one hour per week compared to 3.75 hours in the steady state group and expended only half as many calories during the interval workouts, fat loss, as measured by skin folds, was nine times greater in the interval training group. In the HIIT group, biopsies showed an increase of glycolytic enzymes as well as an increase of HADH activity, a marker of fat oxidation. Researchers concluded that the metabolic adaptations in muscle in response to HIIT favor the process of fat oxidation.
In summary, contrary to hearsay, you do not have to do steady state, low intensity endurance training to enhance fat loss. In reality, fat oxidation while training is only part of the picture when attempting to maximize fat loss. Post-workout, 24-hours, and chronic fat oxidation must be considered.. One final thing to look at is the physiques of 100-meter sprinters. Generally, they perform minimal to no low intensity aerobic activity. They also burn a minimal proportion of fat while training. Think about it.”
In reality, no exercise (aerobic or anaerobic exercise) is required to drop bodyfat. Creating a calorie deficit on a regular basis will result in bodyfat loss. The amount of bodyfat lost or gained also depends on P-ratio. P-ratio is the amount of weight stored or mobilized as protein during weight gain or weight loss. People with higher P-ratios tend to gain and lose higher percentage of weight as protein. Lower P-ratios result in less weight deposition as protein and less weight loss in the form of protein (Henry 2008). P-ratio can be altered to a degree (with exercise, nutrition, drugs) but is largely dependent on genetics.
“Movements that need effort (either for power or for acceleration) are done by muscle fibers that burn SUGAR.” This depends on intensity and duration of movements. There are two anaerobic energy systems—the adenosine tri-phosphate, creatine phosphate (ATP/CP) pathway and the glycolytic pathway. ATP is the basic energy unit for all living things, and the body has a limited amount of ATP in storage. After 3–4 seconds, ATP stores are depleted. After ATP levels are depleted, CP comes into play. CP gives phosphate molecules to adenosine di-phosphate (ADP) to convert to ATP. After about ten seconds of maximal effort, ATP and CP become depleted. Some sources suggest that the ATP/CP system can fuel intense effort for 20-30 seconds (Siff 2000). The glycolytic pathway becomes the primary contributor to muscular energetics after depletion of ATP/CP system. The glycolytic pathway involves the breakdown of glycogen to produce ATP. Pyruvate is the end product of glycolysis, which is converted to lactic acid when insufficient levels of oxygen are present. When sufficient levels of oxygen are present Pyruvate is able to enter the Krebs Cycle. Exercises that are used to enhance power (rate at which work is done) and or acceleration (rate of change of velocity) are generally short in duration and intense. (e.g. plyometrics, Olympic Weightlifting, sprints, throws, speed squats). These movements are dependent on the ATP/CP system. The chemical fuel used in this pathway is creatine phosphate (Janssen 2001). When you say fibers that burn sugar I assume you are referring to glycogen (long chain of glucose stored in muscle and liver) and glucose as sugar. Technically sugar could be one of many different molecules including glucose, galactose, fructose, maltose, sucrose, lactose, or a few others. The newer classification system (described in The Carbohydrate Files Hale 2007) classifies carbohydrates according to degree of polymerization ((Polymerization is a chemical process that combines several monomers to form a polymer or polymeric compound.) and may be divided into three principal groups, namely sugars, oligosaccharides and polysaccharides. Using the word sugar is vague and imprecise.
“So working out vigorously TIRES you and makes you HUNGRY, as you run out of sugar quickly.” This is another example of a logical fallacy “Hasty Generalization”. Fatigue depends on numerous factors. Refer to Skeletal Muscle Fatigue: Cellular Mechanisms by Allen et. al. for a comprehensive discussion of various factors. It is not unusual to see Olympic Weightlifting sessions last 3-4 hrs (which is a pre-dominantly ATP/CP sport). Activities which are primarily glycolytic (I am helping you out here as I think that is what you meant to say above) such as boxing, and mma are performed with rest intervals. If the activities are performed without rest they become lower intensity and more aerobic in nature. The rate at which you run out of glycogen or glucose depends on numerous factors including pre-workout glycogen levels, amount of glycogen you are utilizing, dietary intake while training and so on. Do you realize fatigue can be induced by aerobic activity as well? Guess what sugar (glycogen and glucose) can be depleted with aerobic activity. Aerobic exercise can rely on multiple fuel sources including glycogen, glucose, free fatty acids, intramuscular triglyceride, ketone bodies and protein (McDonald 1998). The storage of carbohydrates is limited while the storage of fats is almost unlimited. Their contributions to energy supply are different and depend on glucose availability, level of exertion, training and duration of activity. What is the effects exercise has on hunger? Vigorous activity often causes decreases in hunger. The effects vigorous workouts have on hunger are variable among individuals.
A study conducted by Erdmann et. al. (2007) investigated the effect of exercise intensity and duration on ghrelin (ghrelin is produced primarily in the stomach- it has been shown to increase appetite and food intake) release and subsequent ad libitum food intake. Bicycle exercise on an ergometer for 30 min at 50 W which was below the aerobic-anaerobic threshold led to an increase of ghrelin which remained unchanged during the higher intensity at 100 W. In a second group 7 subjects cycled at 50 W for 30, 60 and 120 min. Ghrelin concentrations rose significantly above baseline for the respective periods of exercise. The researchers concluded that low rather than high-intensity exercise stimulates ghrelin levels independent of exercise duration. In my personal experience I have noticed a decrease in hunger following high intensity activity. Many of my clients have also reported decreases in hunger following vigorous exercise. It is also important to consider factors other than just exercise that influence food consumption. The following is an excerpt from Freedman MR, King J, Kennedy E (2001) Popular diets: A scientific review. Obesity Research 9(S1): 1–40.): “Many factors influence hunger, appetite, and subsequent food intake. Macronutrient content of the diet is one, and it may not be most important. Neurochemical factors (e.g. serotonin, endorphins, dopamine, and hypothalamic neuropeptide transmitters), gastric signals (e.g. peptides and stomach distention), hedonistic qualities of food (e.g. taste, texture, smell), genetic, environmental (e.g. food availability, cost, and cultural norms), and emotional factors (e.g. eating when bored, depressed, stressed, or happy) must be considered. These parameters influence appetite primarily on a meal-to-meal basis. However, long-term body weight regulation seems to be controlled by hormonal signals from the endocrine pancreas and adipose tissue, (i.e. insulin and leptin).”
On the other end let’s assume vigorous activity causes a huge increase in hunger. So you eat some food. That is not a bad thing. In fact, many athletes strategically plan big meals around training time to take advantage of nutrient timing. I think you would agree that people need to eat at sometime through out the day.
“Vigorous activities will use up more ‘calories’ of energy, than gentle activities do BUT because most of this energy is provided by SUGAR, IT’S A WASTE OF TIME TO LOSE FAT IN THIS WAY. Exercising vigorously to save time is a FALSE ECONOMY” At the end of the day what matters in regards to bodyfat loss is calorie expenditure exceeding intake. Using up more cals during exercise is not a bad thing (when attempting to lose bodyfat). So what do you say to all the athletes and fitness enthusiasts that perform vigorous activities and are lean? Maybe they should not be allowed to lose fat. You said, “IT’S A WASTE OF TIME TO LOSE FAT IN THIS WAY.” That statement is totally irrational and based on your opinion. Is their scientific evidence to support this statement? According to you if we have limited time to workout we should probably just skip the workout; even if we can expect an equal or greater caloric expenditure and fat loss from the workout. Please read the Knowledge and Nonsense excerpt again. When discussing exercise it is also important to discuss exercise compliance. Many trainees are bored when performing “Gentle Movements”. In my opinion one of the key reasons people stop exercising is because they do not enjoy their training regimen. Trainees should be given an option to do what they enjoy.
‘Fat calories’ and ‘sugar calories’ are NOT interchangeable. Doing allot of SUGAR WORK will make you TIRED and HUNGRY so that you need to stop sooner.and you’re likely to eat more. The waste products from sugar burning will ALSO INTERFERE with the processes that release fat from storage and burn it.”I am not sure of what you mean by they are NOT interchangeable so I will address this statement from various angles. If you are implying the caloric value is different between the two you are correct (approximately 9kcals for 1 gram of fat, approximately 4kcals for 1 gram of carbohydrate). If you are saying that some tissues use fat while others use glucose you are correct (or prefer one or the other). If you are suggesting that activity that is primarily dependent on glycolytic activity does not contribute to bodyfat loss you are incorrect. A calorie is a unit of energy. It is the amount of energy or heat that it takes to raise the temperature of one gram of water one degree Celsius (1.8 degrees Fahrenheit). One calorie is equal to 4.184 joules, a common unit of energy used in the physical sciences. The energy derived from foods when they are oxidized in the body is measured in kilocalories (thousands of calories). A kilocalorie is the amount of energy required to raise 1000 grams of water one degree Celsius. Kilocalorie is written as “Calorie” (with a capital C) or it may be abbreviated to “Kcalorie” or “Kcal. The definition of a calorie does not change whether it comes from fat or sugar (as you say) calories. I have already addressed the tired and hungry issue (refer to the information above). I assume one of the waste products you are referring to is lactic acid (or lactate). Contrary to popular belief lactate is not a toxic by- product of metabolism accelerated by glycolytic exercise. Lactate is produced even while resting and can serve as a valuable extra substrate (Siff 2000, Janssen 2001). Lactic acid formed in muscle during exercise can be used to manufacture glucose (gluconeogenesis) in a process known as the Cori Cycle (Siff 2000, Hale 2007). High lactate levels have been associated with a decrease in the burning of fat. I am not sure if this is due to lactate per se, increase in blood acidity, decreased insulin or some other factors. The elevation in blood lactate is acute and has minimal effects on bodyfat loss. After high intensity activity blood lactate returns to normal after approximately 60-75 minutes.
As I indicated earlier the utilization of fat during exercise has little influence on fat loss. Zelasko (1995) stated “although exercise does increase energy output during and after exercise and can expend energy from fat for many overweight persons, excessive caloric expenditure has limited implications for substantially reducing body weight independent of nutritional modifications.” No matter what type of exercise regimen you are following or how many cals and fat you oxidize while training you must create a cal deficit to lose bodyfat.
“Although a vigorous workout will keep your energy use going for several hours afterwards, THE ‘RECOVERY’ PROCESSES ARE MAINLY POWERED BY SUGAR TOO, so this extra ‘metabolism’ isn’t burning much fat.” The human body constantly uses energy (vigorous work or no workout). Once your body stops using energy you are dead. The Recovery process is a different subject matter than what we have been discussing. The key goals for the Recovery phase are to replenish depleted energy sources and remove metabolic by-products. We can further distinguish the Recovery process into various phases including 1- on going recovery 2-rapid recovery 3-delayed recovery (Zalessky 1979). Burke (1999) divides the recovery process into 3 phases including: 1-rapid 2-intermediate 3-longer phase. Substrate utilization during these phases varies. Factors that influence substrate utilization includes 1-nutrients consumed 2-nutrient storage 3- hormones and 4- enzymes. This “extra metabolism” (increase in calorie expenditure) can utilize cals from various sources. Saris & Schrauwen (2004) found there was no difference in fat oxidation between the high and low intensity treatments at 24 hours. In addition, the high intensity group actually maintained a lower respiratory quotient (burned higher proportion of fat) post-exercise.
“If you spend allot of time moving around, you will burn allot of fat. If you move GENTLY enough to keep it up ALL THE TIME, then this will burn the MAXIMUM amount of fat. Any activity that you can do continuously without getting ‘fatigued’ is only using fat for fuel.” What do you mean be a lot? This is a relative term. Allot to you may not be allot to me or vice-versa. No one can move all the time. You are saying if you move too hard and burn too many cals you will not maximize fat burning. The Primary Scientific Data and mounds of anecdotal evidence say you are wrong. Another thing you need to realize is burning a higher proportion of fat does not mean you burning a higher absolute amount. With increased intensity the absolute amount of fat used is often greater. I will say it again the fuel used during exercise is of secondary importance compared to the amount of calories expended over a days time. Some people will burn more cals with lower intensity longer duration activities. Trainees attempting to maximize the fat loss benefits of exercise need to find a balance of duration and intensity that allows them to maximize caloric expenditure.
“By spending allot of time moving around you will stimulate the release of stored fat, so that more fuel is always available. THIS will cause your stored (‘adipose’) fat to be reduced, but it’s a SLOW process. RAPID weight loss is NEVER caused by reduced bodyfat.” For an explanation of how and why fat loss occurs refer to the information I have provided above. Rapid weight loss is due to the loss of glycogen, water, minerals, bodily proteins, adipose tissue, Intramuscular triglyceride and decreased GI tract storage. Big weight loss in the short-term is generally due to a high proportion of water loss.
“You personal trainers really ought to leave the exercise advice to the real experts the exercise physiologists.” This type of statement is common among people who lack argument skills and critical thinking ability. I would recommend that you spend some time educating yourself on critical thinking, logic, research methodology, exercise, and nutrition.
Visit Jamie Hale’s site and purchase his new book (Knowledge and Nonsense: the science of nutrition and exercise) at www.maxcondition.com.
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Burke ER (1999) Optimal Muscle Recovery. Avery.
Erdmann J, Tahbaz R, Lippl F, Wagenpfeil S, Schusdziarra V (2007) Plasma ghrelin levels during exercise- effects of intensity and duration. Regul Pept Oct 4; 143 (1-3): 127-35.
Freedman MR, King J, Kennedy E (2001) Popular diets: A scientific review. Obesity Research 9(S1):1–40.
Hale J (2007) The Carbohydrate Files 2nd Edition. MaxCondition Publishing.
Hale J (2007) Knowledge and Nonsense: the science of nutrition and exercise. MaxCondition Publishing.
Harvey RA, Champe PC (2005) Biochemistry 3rd Edition. LWW.
Henry C.J.K. Quantitative Relationships between Protein and Energy Metabolism: Influence of Body Composition. [Online] 27 March. 2008. http://www.unu.edu/unupress/food2/UID07E/uid07e0r.htm
Janssen P (2001) Lactate Threshold Training. Human Kinetics.
McDonald L (1998) The Ketogenic Diet. Lyle McDonald.
Siff M (2000) Supertraining. Mel C. Siff.
Zelasko CJ (1995) Exercise for Weight Loss: what are the facts? J AM Diet Assoc Dec; 95 (12): 1414-7.