What do you think of people who are naturally slim?

ScreeField wrote: »

Sciencey Answer:

“Calories” are a measurement of energy — it’s just a unit of energy, like Watts or Joules. Or even like: gallons or cups or teaspoons. It's just a unit of measurement. In this case, energy.

Generally, determining how many calories are in food is done by burning the food and calculating the released heat in something called a Bomb Calorimeter. Think of using a hamburger instead of charcoal in your barbecue and calculating how many hamburgers it takes to heat up a cup of water.

1 Calorie = energy it takes to heat up 1 liter (kg) of water by 1 degree Celsius

The math:

Q = mcp^T
= (1kg)(4.18 J/g*C)(1C)
= 4.18 kilojoules
= 1 calorie

So, calories are just energy. However, what your body does with that energy is a whole different story. We started with physics and now we have to shift into chemistry.

When you eat a molecule of sucrose (sugar) what your body does first to it is to break all of the sucrose molecule’s bonds to release energy, but breaking molecular bonds takes energy.

Sucrose has lots of bonds:

C-C bonds: 10
O-H bonds: 8
C-H bonds: 14
C-O bonds: 14

Each of these bonds has different energies:

C-C = 346 kJ/mol
C-H = 411 kJ/mol
O-H = 459 kJ/mol
C-O = 358 kJ/mol

So, you simply add up the bonds and sum the energy per bond.

C-C = 346 kJ/mol x 10 bonds = 3,460 kJ/mol
C-H = 411 kJ/mol x 14 bonds = 5,754 kJ/mol
O-H = 459 kJ/mol x 8 bonds = 3,672 kJ/mol
C-O = 358 kJ/mol x 14 bonds = 5,012 kJ/mol

Total energy it takes to break apart a sucrose molecule is the sum of the above: 17,898 kJ/mol

The next step is to reform those broken bonds into carbon dioxide and water. This also takes energy. And, you have to apply the Principle of Stoichiometric Balance which means, when you are transforming one thing to another with a chemical reaction, you can't destroy its fundamental atoms. You have to end up with the same number of each atom.

The sucrose molecule looks like this:

C12 H22 C11

After digestion, there must be 12 carbons in the final product(s). They can’t go anywhere else. So, to convert the above to carbon dioxide and oxygen, you have to add 12 oxygen molecules to balance both sides of the equation:

C12 H22 O11 + 12O2 = 12CO2 + 11H2O


Then, there’s also the released energy to account for. There are a number of charts online that map metabolic pathways. There are maps for glucose alone that could be printed in 10 pt font and take up entire walls. One of the more well known maps was created by Dr. Donald Nicholson and I believe his map is online. None of the metabolic pathways charts are complete. They are all still works in progress.

If you have access to a glucose metabolic pathway chart, you can see the many many different processes just to use up a glucose molecule — and you can see why there are differences in metabolism of different foods into calories. A calorie is always a calorie (that’s like saying a gallon is always a gallon). However, its the: 1) energy availability of different foods and 2) metabolic processes cause a large variation in results.

cwolfman13 wrote: »

Things like hyperthyroid and other medical conditions aside, "naturally slim" is largely a matter of perception.

GirlonBliss wrote: »

I used to think they were just genetically blessed whereas I would have to work at it for the rest of my life. What about you?

vingogly wrote: »

This is an interesting article on the subject:

http://www.mindbodygreen.com/0-14101/how-naturally-thin-people-eat-move-think-about-food.html