Kruszelnicki - Please Explain

Celery is about 95% water, 2.2% digestible carbohydrates and 1.8% indigestible carbohydrates, as well as insignificant amounts of protein and fat.

BUT there are a small number of kilojoules found in celerynot manybut there are some!

The BMR is a measure of the amount of energy needed to keep you alive when you are resting, in a fasted state, lightly clothed and in an environment with a comfortable temperature.

One way to get to the bottom of this negative kilojoules story is to look at the Basal Metabolic Rate (BMR)a measure of the amount of energy needed to keep you alive when you are resting, in a fasted state, lightly clothed, and in an environment with a comfortable temperature.

Technically, the Basal Metabolic Rate is a measurement of how many millilitres of oxygen you breathe in for every gram of body weight per hour. At rest, human beings typically breathe in about 0.3 ml of oxygen per gram of body weight per hour. Nutritionists measure the BMR by putting a volunteer in an airtight box and measuring how much oxygen they burn up and how much carbon dioxide they generate. These changes in oxygen and carbon dioxide are easy to measure when you consume a huge meal of steak and lots of potatoesand almost impossible to measure when you have a small meal of a few sticks of celery.

About 70% of your total daily energy expenditure is spent in keeping your organs running (e.g. liver, skeletal muscle, brain, kidneys and heart)the BMR, while another 10% comes as a side effect of burning up your food. The remaining 20% comes from physical activity. You can see how, if you increase your exercise just a little and maintain the same food intake, you can lose weight. For example, walking uses about 2000 kJ per hour.

However most of us dont think in terms of O2ml/gm/hrwe think in kilojoules.

The average man uses about 11 000 kJ per day, while women use around 8000. Of course, this will vary according to your weight, age, gender, coffee habit, exercise program, genes that your parents gave you, height, surface area, muscle massand yes, how much you eat.

Back in 1918, J. Arthur Harris and Francis G. Benedict published their paper A Biometric Study of Human Basal Metabolism. They measured the BMRs for 136 men and 103 women and then did a partial correlation coefficient analysis for any factors that might have an effect on BMRa big task in the days before electronic calculators and computers. The equationsthe original century-old ones for the total heat produced in 24 hoursare still a reasonable approximation:

Men, H = 66.4730 + (13.7516 x W) + (5.0033 x S)(6.7550 x A), Women, H = 655.0955 + (9.5634 x W) + (1.8496 x S)(4.6756 x A),

where H is the total amount of heat produced/energy burnt in 24 hours in kilocalories, W = weight in kilograms, S = height in centimetres, and A = age in years. To convert kilocalories to kilojoules, multiply by 4.2. (According to current wisdom in the book trade, each equation in a book reduces the sales by 50%. Thats why Ive cleverly hidden these equations deep inside the chapter and bunched them up so that you can skim right over them and ignore them.)

Surprisingly, just to digest an average meal, human beings increase their BMR by 50%but only for about four hours. In other words, it costs energy to digest the meal. (This might be the basis of the negative energy in celery myth.) Nutritionists call this extra energy the Thermic Effecta kind of Energy Tax. It is also called the SDA (Specific Dynamic Action)but whatever you call it, it takes energy to digest food.

The question ishow much of the energy in the food is needed to digest it? To answer this, you need to know what your body does to get the energy out of the food that you eat.

If you have ever eaten a tough steak, you might think that a lot of the energy that it takes to get the nutrition out of your food comes from chewing. But no, chewing the food takes only 12% of the total energy in the food. The vast majority of the extra energy needed to digest the food is burnt in the gut.