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Calorie Counter: Why "Calories In, Calories Out" Hypothesis May Not Be Telling You the Whole Story

Director Cardiology, Fortis Escorts Hospital
May 19, 2019 6:20 AM 4 min read

We discussed some limitations of the “Calories In, Calories Out” hypothesis here last week, which suggested that assiduously counting one's calories does not help in fat loss or weight maintenance.

Are we really looking at the “Death of the Calorie”, as suggested by a recent cover story of The Economist's 1843 Magazine?


Do calories matter at all?

Of course, they do! But not in the way most people think.

Calories In

Let's look at why calories are thought of to be critical for weight loss/gain in the first place. If we were to give a group of people food prepared with a pre-decided calorie and nutrient content (ratio of carbs: fat: proteins), and control everything else (i.e., work done, calories spent, etc.) without allowing for any extra food, one is unlikely to observe much difference in the weight lost or gained in the short term (within a few days or weeks).

However, there is now sufficient data available that proves that different foods are handled by the body differently. While carbohydrates are quickly digested (within 2-3 hours, with lesser calories burnt), proteins and fats take much longer (about 8-12 hours, with many more calories burnt in the process). 

This implies that net calories gained from eating foods is different from a simple addition of all calories consumed.


Calorie Counter: Why “Calories In, Calories Out” Doesn't Tell the Whole Story

Further, the gut responds differently to different foods. The hormones that signal satiety (a sense of fullness after a meal) are secreted most profusely in response to fat consumption. Therefore, one feels fuller earlier and for a longer duration while consuming a fatty meal vs. A carbohydrate-based meal.

There is data available which proves that the net calorie intake in a day is lower if the fat content is higher than the recommended 30% of all calories (perhaps closer to 40-50%). And that’s how calories indirectly kick in - if we consume more fat and protein compared to carbs, we eat lesser (total calories in a day) and crave food less than if we consume >50-55% calories from carbs (which is the norm in most parts of the World today).

Over the long term, a difference of 100-300 calories per day in the food intake and the extra work done in digesting fats and proteins is responsible for the greater weight loss and fat loss that’s seen with low carb diets.

Also, the real world is not like a controlled study. Here, there are meetings, deadlines, sleepless nights, travel, parties, and much more, which makes it much harder to ensure portion control. The easy digestion of carbs encourages frequent snacking, often leading one to consume unnecessary calories. Carbohydrates are also known to activate brain reward mechanisms, that lead to the pleasurable experience associated with intake of high-calorie, especially high sugar foods, that one craves repeatedly, which is why people get addicted to desserts and colas.


Is it then not better to eat foods that provide early satiety, that we can eat to fullness, not feel hungry or cranky all the time, rather than eating a measured proportion of food that leaves one dissatisfied?

Calories Out

The other side of the equation is exercise. Undoubtedly one of our healthiest activities - exercise, goes a long way in maintaining health and fitness. It also helps in weight maintenance, when accompanied by a good diet. However, despite being intuitive, it comes as a surprise that in the absence of a healthy diet, exercise alone does not help in weight loss, especially as one ages. A study published in 2006 showed that even regular runners would gain weight year on year, unless they increased their running distance by about 3 km per week for men, and nearly 5 km for women.

This suggests that people running in their 20s would need to run marathons every week in their 50s in order to avoid gaining weight - a very impractical idea. The only exception could be elite athletes, who can burn over 1000 calories in their workouts.


Calorie Counter: Why “Calories In, Calories Out” Doesn't Tell the Whole Story

Another problem is the apparent lack of energy or disinclination to exercise that many people face after a few weeks of diet control. Again, the carbs in our diet make everything else (fats and proteins) unusable for providing energy - carbohydrates get digested first while all the other calories get stored as body fat. This means that one has to eat still more to find the energy to exercise or eat less and feel lethargic all the time. Also, as one grows heavier by eating more, the appetite increases further, and a vicious cycle ensues.

Thus, our appetite appears to be a function of what we eat, as is our ability to exercise.

Conclusion: A healthy diet is better than calculating CICO and getting frustrated.

In summary, calories do matter, but different foods are metabolized differently by the body, and thus have variable effects. If you are watching your calories, please watch your food choices first. Moving towards healthy foods may avoid the need for any rigorous portion control or calorie count, which is nearly impossible to achieve in any case. Eating healthy also improves our exercise capacity, making the circle complete.

This is a recurring column published every Sunday. Click here to view my other articles on health, nutrition and exercise. 

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