I've recently started using apps like MyFitnessPal to calculate the amount of energy and nutrients I consume and do some simple number crunching for me. However, all these apps seem to be focused on calorie intake and not much more.

How does fat, sodium, sugar, carbs effect my weight loss diet? Are calories proportional to the amount of fat (etc.) and is therefore an accurate representation? Will simply managing calories be an accurate method of weight control?

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    This doesn't qualify as a full answer, but the calories present in any food is calculated based on the fat, protein, and carbs. nutristrategy.com/nutrition/calories.htm Sep 1, 2011 at 13:19
  • An excellent hit piece against the idea that "a calorie is a calorie" by Rob Dunn has been blogged at Scientific American. Aug 27, 2012 at 20:38
  • This is a question that was on topic when it was originally asked. However, the scope of the site shifted to only allow nutrition questions that are related to exercise specifically. For that reason, this is being closed and retained for historical reasons.
    – JohnP
    Feb 10, 2022 at 15:52

3 Answers 3


Absolutely not. Our metabolism is a complex system of organs working together that dictate how food is used, disposed of, etc. Not to mention, based on your goals and body type, different manipulations to your diet are indeed necessary.

A NIH-funded study tried to suss out the associations between specific foods, lifestyle factors, and weight gain. Its conclusion?

Specific dietary and lifestyle factors are independently associated with long-term weight gain, with a substantial aggregate effect and implications for strategies to prevent obesity.

Other studies are finding similar results (for instance). Our metabolism is too complex to follow the adage, "a calorie is a calorie".

In other words, calories are not the only important aspect of diet. Total caloric intake has an effect, but the foods you're eating and activities you're partaking of will affect your health and weight gain. Perhaps more importantly, the foods you choose to eat will affect how many calories you feel like eating.

The Washington Post summarizes more of the ramifications of this study:

[There are] striking differences in how various foods and drinks — as well as exercise, sleep patterns and other lifestyle choices — affect whether people gradually get fatter.

...[G]etting heavier is not just a matter of “calories in, calories out," and...the mantra: “Eat less and exercise more” is far too simplistic. Although calories remain crucial, some foods clearly cause people to put on more weight than others, perhaps because of their chemical makeup and how our bodies process them. This understanding may help explain the dizzying, often seemingly contradictory nutritional advice from one dietary study to the next.

The problem with focusing solely on Calories is the foods people tend to keep versus cut when they start restricting them.


When you look at Jenny Craig and Weight Watcher's practitioners, the first thing to go is the protein source because they are "high in points" or take up a significant portion of the volume of food the people can eat. This is bad on many points:

  • Protein keeps you satiated longer, so you don't need as much volume
  • Protein is necessary to protect existing muscle mass, or build more muscle mass
  • Excess protein (more than what your body will use) takes a lot of energy to process, in essence raising your metabolism a bit.


Another problem we have is the overemphasis of carbohydrates in western diets. I'll go on a limb and say that carbs are necessary, but definitely not in the quantities most people eat them. For active people (and we are designed to be active), carbs are an important part of recovery and a source of energy. However, they have some negative impacts, and worse if your sedentary:

  • Carbs have the most glycemic impact, and the more processed the carb, the sharper that insulin response is.
  • Insulin prepares your body's cells to accept glycogen, which for active people helps put energy in the muscles. However, in sedentary people, or in great quantities, when the body's cells become saturated, the carbs can only be stored as fat. When this condition exists for extended periods the person becomes insulin resistant, and ultimately diabetic.
  • We are designed to process carbs, but think more in terms of peppers, green vegetables, and fruits.


Our bodies need energy, and it really doesn't matter whether that energy comes from fat or from carbs. The USDA gave fats a bad name, and then later the scientific community had to come back to the defense of certain fats. Most unnatural fats have "trans-fats" which are harmful to the body. However, mono-unsaturated fats like olive oil and fish oil have many good properties that are helpful to the body. Not to mention that certain vitamins we need are fat soluble.


Calories are important, but not as important as a proper balance of the macro-nutrients. Greatly exceeding the number of calories your body burns in a day (through normal metabolism and through activity) forces your body to do something with the excess.

  • Excess protein will get converted to glycogen through a very slow process, but that excess glycogen can cause an insulin spike and ultimately convert it to fat.
  • Carbs are broken down to glycogen immediately, and take a bit less energy to process than protein--but it is most readily turned into body fat.
  • Dietary fat packs the most calories per gram, and takes the least amount of energy to process. However, dietary fat does not necessarily translate to body fat.

Bottom line is that the more active you are, the higher your metabolism gets, and the more Calories you need. Part of this is due to the increased muscle mass that accompanies activity, and part of that is due to how quickly you go through your energy reserves.

Body Type:

Different body types have different challenges, and treating everyone the same is a recipe for disaster.

  • Mesomorph: the stereotypical genetically blessed individual. Hourglass shape for women, perfect V for men. These folks tend to be sensitive to fats, but they can usually work it off pretty quickly.
  • Ectomorph: the pencil shaped body. These folks seem to be able to eat what they want without gaining a pound. A common complaint from these folks is that they can't gain wait. The only way to fix that is to eat copious amounts of food and protein and work hard to turn it into muscle. They just can't seem to hold on to fat.
  • Endomorph: the round bodied person. These folks can't seem to get weight off. They sniff a brownie and gain a pound. Carbs are the endomorph's enemy--especially those highly processed and delicious dessert carbs.
  • Wow amazing answer! Look at my comment on the other answer. You've brought me something no diet ever brought me before -- science!
    – nopcorn
    Sep 1, 2011 at 12:53
  • You might want to remove the comment about "Jenny Craig and Weight Watcher's practitioners". I'm not intimate with the Jenny Craig program, but the Weight Watchers program stresses eating protein over carbohydrates. In its most recent form, there is a daily amount of protein and low-carb vegetables that is virtually mandatory and doesn't count toward "points". Sep 1, 2011 at 13:26
  • Right, that's a recent change forced by the overwhelming evidence of the need for protein. However, I'm not talking about the plans themselves, but what most people who follow the plans tend to do (my mother being one of them). Sep 1, 2011 at 14:09
  • @Berin I can't say what "most people" tend to do. I can only comment on my experience with WW leaders, their groups, and the folks that contribute to the WW Tools development do and what you describe isn't it. Sep 1, 2011 at 18:20
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    Hi @Max! It sounds like you're truly interested in actual body chemistry. For the layman consider the book mentioned in this answer: fitness.stackexchange.com/questions/3238/… (where the graph image is) Hope it helps!!
    – Fattie
    Sep 2, 2011 at 8:45

Calorie Counts are Wrong

John Kiefer debunks the "a calorie is a calorie" argument thoroughly and scientifically, with diligent use of references:

The Idea

Given two diets identical in calorie count, the two must produce the same weight loss or gain regardless of macronutrient content.

The Logic

By the 1st law of thermodynamics that says energy is neither created or destroyed, must, somehow, say that 100 calories of carbohydrates will produce identical effects as 100 calories of fat — or protein for that matter.

The Reality

The idea that a calorie is a calorie actually violates the laws of physics(1-4) and contradicts several well-controlled studies(5-14); you can manipulate macronutrients to cause weight-loss even while increasing calories(15).

(Parenthetical numbers are his references.) He goes on to use the analogy of a car's engine fuel:

Add ethanol to gasoline and your fuel economy goes down. Add other hydrocarbons, like anti-knocking agents, and your efficiency goes up.

The same happens with the human body's use of macronutrients, he argues:

Atwater, the father of the 4-4-9 calorie values for carbs, protein, and fat, respectively, distinguished between physical fuel values and physiological fuel values(16). The first, physical fuel values, is the amount of energy you can get out of food by burning it with oxygen, literally. You throw food in a fancy oven, incinerate then record the total amount of heat released—this is the physical fuel value.

The physiological value is the amount of energy the organism can derive from the fuel, which can be lower or higher.

He goes into specific detail on situations and factors that can cause fat, protein and carbohydrate to change calorie values dramatically. Since at the moment we don't have the ability to easily look beyond physical fuel values at the physiological fuel values, all of our calorie counts are wrong. Technically, calories are still a major factor, but we must be aware that the calories counted on the nutrition label don't have a one-to-one relationship with the calories that we store in our bodies.

Other factors

Food is more than just a video-game power-up. Food is much more complex than calories. Weight control can also be dramatically affected by sleep, stress, exercise, food quality, consistency in diet, gut biota, probiotic intake, sun exposure, vitamin and micronutrient intake, and probably many more. There are no easy answers to eating and living right. The human body is not simple.


Max, you hit on the nature of the debate between the "low-fat" theory (proposed by some departments of the USA government for 20 years or so) and the "low-carbohydrate" theory which was normal science for 200 years and is now promoted by basically all popular books on eating and diet (Carpender, Lutz, Heller, Mackarness, Taubes, Atkins, Eades, etc etc etc).

For example, with myself, I eat only a very modest amount of carbohydrates each day. I simply don't eat "new" foods like potatoes, white bread, sugar. I eat an enormous amount of meat, cream, fats, eggs, and green vegetables. (I mean ENORMOUS - for example I eat at least six eggs a day, just for starters.) My caloric intake would be some huge number if I bothered to measure it. But again, ALMOST NONE of the calories come from carbohydrates (sugars). The calories come only from fat and protein. In my case, the weight is just falling off me (easily one KG per week).

So you ask "Will simply managing calories be an accurate method of weight control?" In fact no, calories have no connection to weight control. You have to slash or indeed eliminate carbohydrate intake to see the weight come off you.

But then again, many people disagree with "pro-fat" (ie, low-carb) thinking, they believe in the USA Government concept of "anti-fat" thinking.

So before the question can be answered, you have to decide which camp you are in. the two camps have absolutely opposite beliefs so it's a difficult question to answer.

Consider reading the book "Why we get fat" by Gary Taubes. (To get "one side" of the situation.) Hope it helps in some way!

  • Thanks for your answer Joe. I like to consider myself a man of science, therefore choosing which "camp" I'm in would require me to research them (minus all the noise and hype) and follow something that actually works and had been proven (by science, not by someone who lost weight). Thanks for your input.
    – nopcorn
    Sep 1, 2011 at 12:46
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    @Max Hi Max, I'm glad to hear you're a scientist! I'm only an engineer and mathematician. If you are interested in regression studies and so on, I urge you to buy the book "Why we get fat" by scientist Gary Taubes. Hope it helps!
    – Fattie
    Sep 2, 2011 at 7:31
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    Eliminating any macro nutrient from your diet, be it fat, carbohydrate or protein is a terrible idea. Eliminating carbs is a bad idea, eliminating fat is a bad idea and eliminating protein is a bad idea. It's rather unfortunate that while you recognise fat isn't an evil you've decided to make the same mistake and replace it with carbohydrate instead.
    – Robin Ashe
    Jun 26, 2012 at 18:22
  • The above answer is mostly complete, however there are a couple erroneous statements. The statement of calories having NO connection to weight control is false. While they are not the sole contributing factor as so many believe, neither are they a non factor. Additionally, the statement of you have to have no carbohydrate intake is also false, as @RobinAshe points out.
    – JohnP
    Jun 26, 2012 at 18:50
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    You show me someone gaining weight on 800 calories a day (or losing on 8000) and I will show you someone with a serious disease process of some kind going on. In an otherwise healthy person, 800 calories a day is in the starvation level, and will produce weight loss.
    – JohnP
    Jun 26, 2012 at 21:13

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