How are calories in foods determined?

Think back to your high school chemistry class and a very fun lab when you got to burn a piece of candy to determine the amount of calories released (I know Conestoga does it, and I hope you were so lucky to experience this lab!). As you may have learned from this lab, a calorie is a unit of energy and it is defined as the amount of energy needed to raise one kilogram of water by one degree Celsius. In terms of nutrition labeling, the calorie we know is actually a kilocalorie since it is 1,000 times larger than what chemists and physicists use in their line of work. If you have ever come in to see me for a nutrition consultation you may notice I write things as "40 kcal, 100 kcal" (kcal= kilocalorie) since that is the way we had to write the units during my nutrition classes and other sciences courses in college.


Previously, calories had been determined by the FDA similar to the way we did it in high school labs, with a bomb calorimeter. The food was burned all the way and the rise in water temperature was then measured. However, this is an outdated method which is not incredibly accurate.


Fast forward to the present method: In 1990 the George H.W. Bush signed the Nutritional Labeling and Education Act of 1990 (NLEA) which required most foods regulated by the FDA have nutrition information on their food label and that all nutritional claims ("low fat", "high fiber") meet the FDA regulations. This law also changed the way the calorie content of foods are determined. Instead of burning the foods, indirect calorimetry is done using the Atwater System... which basically breaks down the food into the energy containing nutrients (fat, protein, alcohol, and carbohdyrate). Fat= 9 kcal/gram, Protein= 4 kcal/ gram, Alcohol= 7 kcal/gram, and Carbohydrate= 4 kcal/gram. Knowing the calorie content per gram of macronutrient, scientists are able to calculate the caloric content of foods. This system is much more complicated than I will explain, but it gives a pretty good idea of the total available calories in a food... the human digestive tract is very efficient and will obtain most of the calories present (unless high amounts of dietary fiber are consumed).


I hope this little science lesson makes you more aware of where the calories come from in your food, I would go into much greater detail of how they determine the specific amount of each macronutrient (e.g: Nitrogen content -> protein estimation), and digestibility calculations, but I don't want to bore you. 

***EXCITING NEWS!!!: If you are a member of the Independence Blue Cross Personal Choice PPO Plan, you can have 6 free nutrition counseling sessions with me over the course of a year! To schedule an appointment, email me at: nutrition@clublamaison.com

References:

"How do food manufacturers calculate the calorie count of packaged foods." Scientific American. 2006, July 31. http://www.scientificamerican.com/article.cfm?id=how-do-food-manufacturers

Agriculture and Consumer Protection. “The Relationship Between Food Composition and Available Energy.” 1981, Oct. 17. http://www.fao.org/DOCREP/MEETING/004/M2847E/M2847E00.HTM

http://www.fda.gov/ICECI/Inspections/InspectionGuides/ucm074948.htm

Maynard, J. The Atwater System of Calculating the Caloric Value of Diets. 1944, Dec. 1. http://jn.nutrition.org/content/28/6/443.full.pdf+html.

Hungry at night? That's going to make your jeans tight!

Many of my clients tell me that for breakfast and lunch eat very healthy and are able to control their calorie intake. However, later in the day, and especially after dinner, they get hungry and start craving carb-rich foods (whether it be ice cream or tortilla chips). Many people with this tendency get themselves into trouble,  because for some reason most people feel like calories after dinner don't count. If this is the case with you, you could be consuming several hundred more calories than you've accounted for during the day, and you may end up sabatoging your weight loss goals.

Carb-cravings and late night eating are a tell-tale sign that you are not consuming enough calories early in the day, and that your body is seeking more nourishment. You are probably missing out on key nutrients and your body is trying to tell you to get them in! So, I recommend you evaluate how many calories you are eating every day and determine if this is enough to sustain you. My rule of thumb for most women is never to go below 1500 calories, and for men, never below 1700 (unless you are a very small, inactive person). After you have established that you are eating enough calories to support yourself, evaluate whether you are consuming enough carbs and protein early on in the day. If you are eating an omelet for breakfast and a salad for lunch, chances are  you need a lot more carbs to keep you feeling satisfied. Note: CARBS ARE NOT BAD!!! I cannot emphasize enough that carbohydrates are critical to having a healthy diet, and some of the healthiest foods are mostly carbohydrates: oat bran, sweet potatoes, barley, kidney beans, etc.

I had a client come in for a follow-up yesterday and she told me since we changed her meal plans she is feeling so much more energetic during the day and does not get hungry mid-afternoon anymore. What did I do? I recommended that she consume more protein with breakfast, and add more starches with lunch.

So, if you are a person that binges late-day or night, here are my steps to ameliorate the problem:
1. Determine if you are eating enough calories for your body and activity level (if you don't know the correct number, come see me!).
2. Determine if you are eating enough calories, protein, and carbohydrates during the day when you are most active
3. Determine if you are eating enough protein each day.
4. Determine if you are eating enough carbohydrates each day.
5. If you found that you are not eating enough for questions 1-4, try to add protein and starches to breakfast and lunch. Sample meal ideas:

Breakfast: 1 egg + 2 egg white omelet with spinach and a slice of multigrain toast or oatbran with flax, blueberries, and soymilk or whole grain cold cereal with skim or 1% milk
Snack: Yogurt with fruit or Kelly's Healthy Trail Mix (recipe to come later)
Lunch: Salad with chicken and whole-grain pita and an orange on the side or turkey sandwich on whole grain bread with fruit and yogurt on side
Snack: Apple & Peanut butter or cottage cheese with fruit
Dinner: Sweet potato, salmon, kale & broccoli or stir fry (mixed veggies, brown rice, chicken)
PM snack: cottage cheese and fruit or soy/almond milk or yogurt & flax

Other tips:  Brush your teeth & use mouthwash after dinner or chew a piece of mint gum to discourage you from eating more.

Don't let the late night eating get out of control. If you need help with your diet, I recommend you see a dietitian ASAP. Just a pound of weight gain each year can put you at an increased risk for many diseases (heart disease, diabetes, cancers, etc) ... plus an extra pound a year can add up to a LOT considering the average age that people are living to nowadays.

Good luck!