You use both fat and carbohydrates for energy during exercise, with these two fuels providing that energy on a sliding scale. During exercise at a very low intensity (e.g., walking), fat accounts for most of the energy expenditure. As exercise intensity increases up to the lactate threshold (the exercise intensity that marks the transition between exercise that is almost purely aerobic and exercise that includes a significant anaerobic contribution; also considered the highest sustainable aerobic intensity), the contribution from fat decreases while the contribution from carbohydrates increases. When exercising just below the lactate threshold, you are using mostly carbohydrates. Once the intensity of exercise has risen above the lactate threshold, carbohydrates become the only fuel source.
If you exercise long enough (1.5–2 hours), your muscle carbohydrate (glycogen) content and blood glucose concentration become low. This metabolic state presents a threat to the muscles’ survival, since carbohydrates are muscles’ preferred fuel. When carbohydrates are not available, the muscles are forced to rely on fat as fuel.
Since more fat is used at low exercise intensities, people often assume that low-intensity exercise is best for burning fat, an idea that has given birth to the “fat-burning zone.” However, while only a small amount of fat is used when exercising just below the lactate threshold, the rate of caloric expenditure and the total number of calories expended are much greater than they are when exercising at a lower intensity, so the total amount of fat used is also greater.
For fat and weight loss, what matters most is the difference between the number of calories you expend and the number of calories you consume. Fat and weight loss is about burning lots of calories and cutting back on the number of calories consumed. For the purpose of losing weight, it matters little whether the calories burned during exercise come from fat or carbohydrates.
Go Very Long
Long runs or bike rides (≥ 1.5–2 hours at 65%–70% max HR) that stimulate mitochondrial synthesis and promote the depletion of glycogen threaten the muscles’ survival, since carbohydrates are muscles’ preferred fuel. In response to this threat, muscles “learn” how to use fat more effectively and over time become better fat-burning machines.
Friday, April 8, 2011
Meditation Lowers Blood Cortisol Levels
Stress triggers many physiological changes in the body through the “fight or flight” response. When stress levels are high, levels of the hormone cortisol released into the bloodstream are also high. Studies confirm that chronic stress is associated with increased fat in the abdominal area, higher concentrations of blood sugar and insulin, higher blood pressure and higher levels of cholesterol—conditions that are associated with metabolic syndrome and that increase the risk of heart disease.
A recent small study published in the Annals of the New York Academy of Sciences (2004; [1032], 211–15) suggests that older women who regularly practice meditation may have a reduced cortisol response to stress—and that the longer a woman has been practicing, the less likely she is to react to stress with high levels of blood cortisol.
Walton and colleagues studied 30 women, 16 who were long-term practitioners of TM and 14 controls, all between the ages of 65 and 92 years. The subjects ingested 75 grams of glucose in order to stress their systems metabolically. Cortisol levels were measured before and after administration of the stressor. The researchers found that cortisol levels rose much higher and with greater speed among the controls than among the meditators. Moreover, the longer a subject had practiced meditation, the lower her cortisol response was. The study authors theorized that this lower cortisol response may reflect improvement of the endocrine system regulation and recommended that more research be conducted.
A recent small study published in the Annals of the New York Academy of Sciences (2004; [1032], 211–15) suggests that older women who regularly practice meditation may have a reduced cortisol response to stress—and that the longer a woman has been practicing, the less likely she is to react to stress with high levels of blood cortisol.
Walton and colleagues studied 30 women, 16 who were long-term practitioners of TM and 14 controls, all between the ages of 65 and 92 years. The subjects ingested 75 grams of glucose in order to stress their systems metabolically. Cortisol levels were measured before and after administration of the stressor. The researchers found that cortisol levels rose much higher and with greater speed among the controls than among the meditators. Moreover, the longer a subject had practiced meditation, the lower her cortisol response was. The study authors theorized that this lower cortisol response may reflect improvement of the endocrine system regulation and recommended that more research be conducted.
Tuesday, April 5, 2011
No pain no gain?
People today are becoming fitness freaks and are ready to explore several options to keep healthy. It seems as if they are on a continuous search for new, more advanced and beneficial regimes.
Unfortunately, what you hear is not always true. Here is the most popular myths pertaining to fitness:
1. 'No pain, no gain'
Pain is a warning sign that indicates any potential harm to the body. You should not feel any type of pain during or after exercise. If you feel pain, it means you are on the wrong track. One must be able to differentiate between pain and discomfort. When you begin a new exercise, an initial mild discomfort is normal and it is due to muscle soreness (DOMS).
Don't force your body to continue with a workout if you perceive any kind of pain. Remember, if there is pain there will be no gain. With a proper and planned exercise regime and a maintained exercise log, one can gain without pain.
Unfortunately, what you hear is not always true. Here is the most popular myths pertaining to fitness:
1. 'No pain, no gain'
Pain is a warning sign that indicates any potential harm to the body. You should not feel any type of pain during or after exercise. If you feel pain, it means you are on the wrong track. One must be able to differentiate between pain and discomfort. When you begin a new exercise, an initial mild discomfort is normal and it is due to muscle soreness (DOMS).
Don't force your body to continue with a workout if you perceive any kind of pain. Remember, if there is pain there will be no gain. With a proper and planned exercise regime and a maintained exercise log, one can gain without pain.
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