Energy expediture and its role in weight gain and lose

We use our net energy for maintenance (average daily expediture is 2000 kcal for female, 2500 kcal for male), for physical activity (exercising) and for growth. Our daily energy expediture can be higher or lower, depending on body size, illness or physical activity. The maintenance part is essential for our survival (things such as heart beat, brain function, respiration).

Now i will introduce some new terms. Basal maintenance in fasting state is called Basal Metabolic Rate (BMR). To this we will add the energy cost of digestion and absorption (dietary induced thermogenesis - approx. 10% of the caloric value of the meal). BMR covers 60-70% of the daily energy expediture and it is different between individuals, depending of the lean body mass (body mass remaining after we subtract the fat). Tall people with lot of muscle will have a much higher BMR than short fat people.

Physical activity is measured by PAL (Physical Activity Level) and is defined by the daily amount of physical activity of a person. This vary from 1.4 for sedentary people to 2.0 for athletes, with 1.6-1.7 being the average Joe. Can be measured though the oxygen consumption (indirect calorimetry).

As for growth, we will think at the net energy required to make extra tissue. It is close to zero for weight stable adults, relevant for children and pregnant women.

We store energy as fat, a dense and easy to use form of energy. The average amount of fat stored by a normal individual is 90.000 kcal (enough to support us for 30 days of fasting, but this can last for months if you are obese). Average amount of proteins stored is 36000 kcal, but you can use only 12000 kcal in case of emergency, before you start to compromise some of the normal body functions. Average amount of carbohydrates stored is 1400 kcal in the muscle and 350 kcal in the liver as glycogen, and it is used to maintain the blood glucose level in between meals.

When the energy intake is exceeding the energy expediture, the excess is stored as fat and we will experience weight gain. After a certain margin (let's say 600 kcal), the body weight tends to level off after a while, even if initially will go up, as the energy expediture also increase with the weight gain, until a new equilibrium is reached at a higher body weight. Why, you will ask? Because the BMR will increase as the body weight increase, even if the BMR is mainly determined by the lean body mass. The energy cost of the physical activity will be higher with greater body-weight (you need more energy to use your body as your overall body mass increase.

The opposite happens if we lose weight. Weight loss is rapid at first, but progressively slows down as the energy deficit decrease. Losing weight, the energy expediture decrease as well as BMR and the energy required for physical activity decrease, until a new equilibrium point is reached. This is the reason why every diet will work well at first, but lose efficiency over time.

Next post will be about weight management and obesity.

Energy value of nutrients

Today we will talk about the energy value, Atwater factors, metabolizable energy and kilocalories.

Our energy value come 30-70% from carbs, 15-50% from fats and 10-25% from proteins. The Adwater factors are:

-gross energy - all the energy present in the food products (not all is available)
-digestible energy - amount of energy absorbed, dependent of the digestibility of the food (carbs 98%, fats 95%, proteins 92%)
-metabolizable energy - what is left after accounting the energy in feces and urine.

So, the gross energy is made by the digestible energy and the one not available. The digestible energy is made by the metabolizable energy and the energy eliminated through feces and urine. The energy eliminated is mostly made from proteins (30% of it as urea). The calories we see on the food package are in fact equal with the metabolizable energy.

In terms of kilo-calories (kcal), we have the carbohydrates and proteins with 4 kcal, fats with 9 kcal and alcohol with 7 kcal. In terms of dietary fiber, the insoluble one is subtracted from the carbs content, and the soluble ones have 4 kcal per gram. According to the EU rules, all the fiber is considered to have 2 kcal per gram.

The Atwater factor is an average, but in real life the digestibility can be different. For example, from the thermic effect of food point of view (dietary induced thermogenesis), the transient increase in energy expediture following meal consumption, caused by digestion, absorption and processing of the nutrients, it is higher for proteins than for carbohydrates and fats. Also, proteins, fats and carbs have different effects on hunger and satiety.

In conclusion, the traditional view that all energy is equal regardless of the source (a calorie is a calorie) is overly simplistic and often wrong in real life.

Next post: energy expediture.

Carbohidrates II (About fiber and lactose-intolerance)

Let's continue to explore the carbs story.

As i said in a previous post, there are some carbs that cannot be digested. They are named fibers, and they can be water soluble and insoluble.
-Soluble fibers are known to lower blood cholesterol  (reducing the risk of heart disease), slow glucose absorption (protecting against type 2 diabetes) and hold moisture in stools (preventing constipation).
-The insoluble fibers are known to increase fecal weight, speed fecal passage and provide bulk and fullness feelings when eaten.

At first, in the past decades, researchers believed in a relation between fibers and colon cancer, but recent cohort studies proved that untrue. However, an increase in fibers can improve health, only because we are not having the right amount every day.


Lactose intolerance

What is lactose? Lactose is the sugar from milk, yogurt and dairy. Lactose intolerance is manifested through abdominal pain, bloating, gas development and diarrhea. Is is the result of a deficiency of an enzyme present in the gastro-intestinal tract, called lactase. Lactase can break the lactose in its primary components - glucose and galactose. Anyway, as you age, your body gradually lose the ability to produce lactase. Most of the people around the world will become eventually lactose-intolerant. Globally,most of the Northern and Western Europe is lactose-tolerant, while most of the Asia is lactose intolerant.

Does this means complete elimination of milk and dairy? Not always, sometimes yogurt is better tolerated than milk, but if this is not the case, you can always use lacto-free milk (made from soy or almonds, for example).

How to avoid getting fat in few easy steps (part 1)

This is a story of love, a Valentine's Day special, the story of interdependence and attachment between two main macro-nutrients, let's call them carbohydrates and fats.

Carbohydrates can be simple and complex. The simple ones can be classified in monosaccharides (glucose, fructose and galactose) and disaccharides (maltose, sucrose and lactose). The complex ones are glycogen, starchi and fibers.

During digestion, the starch is broken to same degree, under the action of the amylase enzyme, secreted by salivary glands. When the carbohydrates reaches the stomach, the amylase is inactivated by the acidic medium. The digestion continues in the duodenum, under the action of the pancreatic amylase (an enzyme secreted by the pancreas). The starch is broken in maltose, sucrose and lactose. They are transformed in fructose, glucose and galactose under the action of enzymes such as maltase, sucrase and lactase).

Absorbed in the blood stream, the monosaccharides (glucose, fructose and galactose) are then processed in the liver, where almost all the fructose and galactose is used, and a big part of the glucose goes back in the blood stream, in direct relation to the blood sugar level (glucose level).

When glucose level goes up, the pancreas is secreting the insulin hormone, the role of insulin being to transform the glucose from the blood stream into glycogen, and to deposit the glycogen into the muscle and in the liver. After this process the blood sugar level is decreasing. Because of this action, the pancreas is secreting another hormone called glucagon, to break the glycogen from the liver into glucose, and when the liver deposit is finished (for example during a period of fasting), the glycogen from the muscle is used. The glycogen deposit from the muscle it is also used to generate energy when we are exercising. If we finish both of them (the deposits from muscle and from liver), the muscle is used for glycogen and we lose weight.

If both the deposits are up to 100%, the glucose is transformed into fat. But the fat is never transformed back into glucose.

Conclusions:

Fasting and exercise are helping us to deplete the glycogen deposits, so the glucose will not be transformed in fat. (Search on Google about intermittent fasting)

If we fast and exercise too much, we will lose weight (but this will be muscle weight and not fat weight).

It is possible to eat plenty of sweets, as long as you are having a fasting period right before/after, or you exercise, or both. (This is by far my favourite conclusion)


(More to come soon - this is an excerpt from the future second edition of the book The Macronutrients Pocket Guide, written by me, of course )

Take care of your glycogen deposits,
G.