Posted 19 June 2008 - 12:14 PM
yeah, the weight X 7 is completely wrong and a dangerous thing for them to be promoting, especially since if you eat too little for your weight and activity level, you will lose muscle mass, which no one wants!
Not to mention the fact that you cannot possibly get all the nutrients your body needs with so few calories. Generally speaking, most women need around 1800 calories per day to get their nutrients met. People way under-estimate how many calories they actually take in every day, and this is usually why we have a hard time losing. Most people also over-estimate how many calories they burn working out. Cardio machines are notorious for giving false readings, because what you burn as an individual varies greatly. Even the ones that ask you to enter your weight can be off by a few hundred calories because they don't take into account body composition. Someone who is 150lb and 18% fat burns more calories at rest than someone who is 150lb and 25% fat, but those machines can't measure that.
And what they're saying about the 20 min of exercise is kind of true, but not completely accurate. Essentially, during the first 20 minutes (for MOST people, it really depends on you as an individual and how you metabolize food), you are burning glycogen stores, not fat. The fuel that is stored in your muscles gets used first (glycogen that was converted from carbs). Once you have used the glycogen stores, your body then starts burning fat for fuel. It is less efficient at doing this, which is why it always turns to glycocen for immediate energy first. However, you can only work out for so long on your fat stores before you become too tired; this is why marathon runners and endurance athletes need to take power gels or other quick-release carbs during races- once their glycogen stores are completely depleted, it is dangerous.
The average person will not completely deplete their glycogen on a regular workout though.
The part that is too bad about this is that it might discourage people who can only work out for 20 min a day into thinking that it's not worth it if they can't do at least 40. Obviously 40+ min of cardio is optimal, but the reality is that you continue burning calories after you workout, and you burn more calories AT REST post-workout than you do AT REST without working out. So even though you may have stopped working out after 20 min, you are burning more calories sitting there than you would have been if you did nothing.
I guess it just seems somewhat discouraging when there is such an obesity problem in North America for people to be told that 20 min isn't enough. Every little bit helps, and for someone who is really discouraged, 20 min is a great start!
Colin in I in 2005 when we fell in love with Maui!
