One of the easiest tricks and highly trusted method to lose weight is to eat less. Its logical to think that if you eat less you will lose weight.
And this means you have to count your calories and reduce your daily intake. Most dieticians recommend this.
However, science keeps questioning every notion even if it has been set a couple of months back; some researchers and doctors now say that weight loss is no more about counting calories.
And the argument is whether a calorie is a calorie or not?
A Calorie is a Calorie
A calorie is a unit to measure the energy value of food. 1 food calorie is equal to 1kcal or 1000 calories.
1 calorie is the amount of energy required to raise 1 kg of water from 15 to 16 degree C.
When you look at the statement you would say yes a calorie is a calorie just like a kilogram is a kilogram.
But this is not where it stops.
As per thermodynamics, a calorie is a calorie irrespective of the source.
This view is extended to weight loss when they say you should cut down your calories irrespective of their source.
Some researchers feel that this statement conflicts with the first and second law of thermodynamics (Conservation of energy and Law of dissipation).
This is because diets with equal calories produce different results in terms of weight loss.
Or different foods providing the same number of calories have a different effect on body weight.
Biologically speaking, a calorie is not a calorie. So it is felt that rather than counting calories, one should focus on the macronutrient composition of the calories.
Why is it felt that ‘A calorie is not really a calorie’?
There are several reasons why the statement is disputed and we will be going over them one by one.
Our body does not extract 100% of the energy provided
Energy obtained by combustion or breakdown of food is not the same as energy available to the body after consumption of the same food.
This concept is known as metabolizable energy.
Scientists such as Rubner and Atwater conducted a number of experiments before giving us these values :
- Protein: 4 kcal/g
- Fats: 9 kcal/g
- Carbohydrates: 4 kcal/g
These are average values and errors can result due to the difference in chemical structure.
Now, these values when applied to a mixed diet tend to overestimate their metabolizable energy.
For example presence of dietary fibre can affect metabolizable energy of a diet since it decreases transit time of food in the intestine, increases bulking and its energy content is liberated by fermentation.
This affects digestion and absorption.
These values overestimate metabolizable energy of diets high in nonavailable fibre and diets high in available fibre by 7.0% and 2.6%.
In simple terms, all carbohydrates do not provide 4kcal/g.
Buchholz and Schoeller discuss this point in their paper where they say that this difference could account for 0.3-0.6 kg difference in weight loss over 12 weeks for meals differing in fibre content but providing 1500 metabolizable kcal/day.
What does this mean? The number of calories provided by gram of each macronutrient are average values and these values can change depending on the structure of macronutrients. Like fibres are carbohydrates but they will not provide you 4kcal/gram and this difference could be held responsible for different weight loss results by isocaloric diets. However a few scientists state this difference is too minor.
Different nutrients require different amounts of energy to be processed
Total energy expenditure consists of resting metabolic rate, thermic effect of food and energy expended in physical activity.
Diets differing in macronutrient composition can produce differences in energy expenditure.
Thermic effect of food is the heat required to process the food.
Thermic effects of nutrients are approximately 2–3 % for lipids, 6–8 % for carbohydrates, and 25–30% for proteins. This is why it is generally claimed that proteins increase metabolism.
In fact, a few studies have shown that high protein diet brings about a 40-50kcal/day increase in resting metabolic rate.
Interestingly a study comparing the effects of different diets on energy expenditure during weight maintenance reported that reduction in energy expenditure was maximum with low-fat diet followed by low glycemic index diet and very low carb diet.
Ingestion of processed foods reduces energy expenditure by 50% in comparison to whole foods.
However, some say that for 1500 kcal diet, a high protein diet would cause 41kcal/day increase in energy expenditure which would translate to a 0.44kg increase in weight loss in 12 weeks.
This rise in metabolism is not significant.
What does this mean? Protein is one such macronutrient which raises metabolism. Additionally different macronutrients require different energy to be digested and used; the one that requires most energy is protein. Diets rich in protein have this advantage of raising metabolism, though some scientists claim that this rise in metabolism is not significant in terms of weight loss as depicted in duration of studies.
Low Carbohydrate diets are metabolically advantageous
Low carb diets were derived after the failure of low fat diets.
Greene et al conducted a study where weight loss results in three different but isocaloric diet groups were as follows:
- Low carbohydrate: 23 lbs
- Low carbohydrate + 300kcal : 20 lbs
- Low fat: 17 lbs
These results suggested that low carb diets have a metabolic advantage.
Studies comparing low and high carbohydrate diets also show that weight loss is greater in low carb group.
A few reasons why low carb diets are said to be metabolically advantageous are:
- Different biochemical pathways involved in processing different nutrients; very low carb diet puts your body in a state of ketosis
- Hormones at play eg: Insulin controls blood glucose levels
- Low carb diets are generally high in protein which raises metabolism
Anssi H Mannien gives a critical review of low carb diets in his paper and also demonstrates that low carb diets cause better weight loss in comparison to other isocaloric diet and most of the weight loss is fat.
Buchholz and Schoeller argue that the manipulation of carbohydrate and fat keeping protein constant does not alter total energy expenditure and they suggest other factors such as inaccurate record of physical activity, loss of water weight and errors in reporting actual intake (those consuming low carbohydrate diets might not be complying with the diet and hence consuming lesser calories) could be responsible for the different results.
Also in long term, low carb diets produce almost the same results as any other diet. (Read: Atkins Diet for weight loss)
What does this mean? Low carb diets are thought to be metabolically advantageous because apart from being low in calories they also initiate a different set of reactions which stimulate fat loss since fat is used as fuel during lack of carbs. So for the same number of calories weight loss is larger. Some scientists counter this argument by suggesting other possible explanation like loss of water weight, loss of fat free mass, inaccurately reported energy intake etc.
Different foods generate different effects on body weight
A common example that is cited in context to this topic is 100 calories of candy and 100 calories of broccoli have different effects on our body.
100 calorie of candy will cause your insulin to spike, facilitate storage of visceral fat and increases the risk of cardiovascular disease.
On the other hand, 100 calorie of broccoli which provides carbohydrate in the form of fibre and additionally provides vitamins, minerals and it will definitely create a risk of metabolic disease.
Sugar if taken in excess can be toxic and addictive. Glucose in sugar is metabolized whereas fructose is converted to fat.
Sugar-rich foods raise blood glucose very fast and to control it insulin spikes. The immediate decline in blood sugar causes your brain to give signals that you are still hungry.
This further leads to insulin resistance and metabolic diseases.
So calories of food rich in fructose syrup are only likely to make you gain weight and are also unhealthy.
Satiety index of foods differs. Protein is very satiating compared to other nutrients.
Fructose elicits weak satiety signals which are why soda or fructose enriched beverages always leave you hungry irrespective of the amount consumed.
You can never overconsume whole foods such as vegetables and fruits.
What does this mean? Different foods have different effects. You can have only a limited amount of fruits but you can easily overconsume candy and chocolate. Sugar in fruits comes with vitamins, minerals and fibres whereas sugar in candy increases your risk of cardiometabolic diseases.
Does this mean that calorie counting does not count?
For us common people it really doesn’t matter whether a calorie is a calorie in thermodynamic terms.
What matters is how it will affect our body weight. And when you go over the above-mentioned points you do feel that in biological terms a calorie is not a calorie and low carbs diet definitely provide more weight loss per calorie in comparison to other isocaloric diets.
Mark Haub, a professor of human nutrition at Kansas State University conducted a little experiment in which he went on a Twinkie diet for 10 weeks where he ate less than 1800 calorie a day and that was from junk food.
He lost 27 pounds in 2 months.
2/3 of his daily intake came from junk food. He also consumed a protein shake and multivitamins regularly and a can of vegetables on and off. His good cholesterol levels rose, bad cholesterol levels declined.
Prior to this experiment, he ate a healthy diet but he was still overweight and was eating too much. You can read more about this right here.
The idea was not to recommend a Twinkie diet but the professor intended to show that counting calories to lose weight still matters.
A plausible explanation for the better metabolic profile is that being obese is the root of metabolic diseases and losing weight ameliorated the conditions.
However, the professor himself is confounded with the results to give any justifiable explanation.
Conclusion
When speaking about energy, a calorie will always be a calorie wherever it comes from.
But how that calorie is utilised in our body and how it affects our weight is difficult to describe in terms of laws.
Also, every individual’s body is different so some diets suit you some don’t.
Low carb diets make you lose water weight, high protein diets make you gain weight in form of muscle, if you suffer from diabetes or hyperinsulinemia you are likely to gain weight even with fewer calories, real-life settings are different from clinical settings and there are many such factors.
Research studies, clinical trials and individual experiments each give their unique result and my work was to present it to you.
So we can make the best of both worlds: Count your calories and ensure they come from healthy sources.
That would include incorporating protein, cutting out on sugary foods, eating veggies and fruits etc. Keep browsing our website for more updates.