Very good book. The style is a little wordy for me. Similar to 'The Power of Yoga', I'd have preferred to have more bullet points and less history of scientific discoveries. Therefore, I summarized the key points myself:
1) Inactivity is the greatest public health threat of this century. A great deal of the physical effects that we once thought were caused by aging are actually the results of inactivity.
2) Although 'Health' and 'Fitness' are often automatically joined together, they are different things. 'Health' is a slippery term, often defined by its absence (it's 'unhealthy' to have high LDL cholesterol, high blood pressure, high blood sugar, a wide waist or actuall illnesses, from cold to cancer).
Physical 'Fitness' refers to cardiovascular or cardiorrespiratory fitness(includes measures of lung function). It is a measure of how efficiently you transport oxygen to laboring muscles to maintain movement. A fit person has a robust heart, strong lungs and sturdy muscles. But it doesn't mean he is 'healthy' (he can still have high cholesterol or ulcers).
3) How little activity can people get away with? The best available science indicates that, in order to improve your health, you should walk or work out lightly for 150 minutes a week. You can split them almost any way you want. 30 minutes a day can be split in 3 walks of 10' each. Other option is to do 75 weekly minutes of more vigorous aerobic exercise plus weight training twice a week.
4) Almost all of the mortality reductions are due to the first 20 minutes of exercise, which drops your risk of premature death by 20%. (If you triple that minimum level, you drop your risk of premature rate further, but only by another 4%). However, this is true if you're looking for health benefits, but not if your objective is fitness.
5) If your objective is to improve fitness and performance, you must overload the muscoloskeletal and cardiovascular systems, i.e.: you will have to push your body somewhat, increasing the intensity or frequency of your usual workouts. Aerobic exercise (endurance) is the wellspring of fitness and may be the single most important determinant of how long you live.
6) Exercise has been endurance-centric for quite some time, but now there is evidence strength training is also important. It changes the dynamics of aging by combating loss of muscle mass (sarcopenia) and building bone, which we start losing at middle age. Squats are considered by some scientists the single best exercise. And Yoga (or Pilates and its variations) have been shown to prompt muscular remodeling almost as readily as working with weight machines does.
7) The benefits of exercise appear to be curvilinear: they rise precipitously when you first start exercising, level off as you do more and, at some point, drop if you overdo things (although when the break point occurs differs by person). And then you may develop injuries and need to stop for a while. But the good news is that reductions in exercise don't have to strip you of your hard-won health and fitness gains as long as you don't stop completely (once a week seems to be enough until you can get back on track).
8) Sitting adversely affects the health of even the well-exercised. Even if you exercise one hour a day, it does not counteract the ill effects of sitting for the rest of the day. It's important to break up the long hours of sitting, even if it's for a two-minute stroll. This was probably the most shocking discovery for me, who felt very virtuous by exercising every morning before my one hour drive to work followed by 8 hours sitting on a chair!
9) Exercise by itself is pretty useless for weight loss since, as a species, we're astonishingly efficient at compensating for the loss of calories. It was discovered that, for example, people relying on exercising to burn out calories sometimes, without deliberate intent, begin moving less during the rest of the day. The body, and especially in the case of women, also has hormonal mechanisms to maintain body fat, such as recalibrating the appetite and increasing the desire to eat after exercise, as well as affecting the rate at which the body burns fuel (acylated ghrelin, leptin and insulin are the key hormones intervening in the process).
10) However, although exercise doesn't aid much in weight loss, it is helpful in weight control or maintenance in the long term (even brisk walking). Exercise not also helps to reduce weight regain but to keep visceral or abdominal fats in check. (They contribute to metabolic problems, diabetes and heart disease).
11) If you want to lose weight: work out before breakfast and include eggs in your breakfast. Emerging evidence also suggests that, unlike bouts of moderate-vigorous exercise, low-intensity ambulation, standing, etc. may contribute to daily energy expenditure without triggering the caloric compensation effect. Just get rid of your chair!
12) Exercise helps to get better brainpower, pushing the onset of dementia by several years. It has a prophylactic effect against the buildup of anger and helps handle stress. It speeds the brain's production of serotonin alleviating anxiety and depression. And it has great influence on kids' brains, improving test scores and IQ.
People who have been active in their twenties, no matter what their activity levels are now, have longer telomeres, a reliable marker of younger cell age. (Telomeres are the minuscule protective caps at the end of the DNA strands, often compared to the tips of shoelaces and serving the same purpose: to prevent fraying and tattering).
Those points summarize my key takeaways from the book. It's also interesting that the author questions some myths, such as the need for stretching and warming up, the benefits of massage (she says it actually impairs the removal of lactic acid) or immersing in ice to ease muscle soreness. There is no correlation at all between wearing the proper running shoes and avoiding injury. You don't need special food or drinks: real food is fine and chocolate milk is the best post workout drink. Vitamins not only are not helpful, but they may undercut the exercise's benefits (since they prevent the induction of molecular regulators of insulin sensitivity and endogenous antioxidant defense - the body 'decided' it wasn't needed). The best remedy for muscle cramps is pickle juice!
And, finally, avoid over drinking: you don't need to stay ahead of your thirst. If you're thirsty, drink. If not, you're sufficiently hydrated. Hyponatremia (water intoxication) is what causes deaths at marathons, not dehydration.