Understanding the Discrepancy Between Macronutrient Totals and Caloric Sum

In a Nutshell

There isn’t a straightforward match between macronutrients and total calories.

The Root of the Discrepancy

This table summarises the rule of thumb for converting macros to calories. But when this table is used the calories often mismatch with actual intake.

This Discrepancy is not a miscalculation or mistake. It is an intentional. Here is the more accurate representation of this table.

The actual energy derived from macronutrients can vary significantly depending on the food source. This is where Atwater Specific Factors come into play, offering more precise values:

Summary

While the general caloric values (Atwater General Factors) offer a close approximation, the specific factors are inherently more accurate for certain food sources. The general values are meant to be a practical estimate rather than precise measurements. For in-depth research, you can refer to the detailed tables and figures in this doc: - Energy value of foods (circa. 1973) Look for table 13 on page 25.

The Atwater Specific Factors are more accurate for specific foods than the Atwater General Factors, which are just approximate estimates.

So What Does It All Mean?

Cal: A measure of energy is different for each type of macronutrient. But also different for every source of macronutrient. Further, some sources are easier to estimate than others. The 4-4-9 is an inaccurate but useful rule of thumb.

As for what is the authority in determining the calories, it is: 1. digestibility 2. Biochemical composition of nutrient

Here is an example:

Summary

As shown in the table, the energy derived from each macronutrient can vary greatly depending on the food source. These differences are due to factors such as how well the food is digested and the specific attributes of the nutrients it contains.

What do Atwater General Factors Not Account For?

The Atwater General Factors don’t account for the energy in fiber, sugar alcohols, and ethanol. Here’s a breakdown:

Summary

• Insoluble Fiber: Technically a carbohydrate but yields 0 kcal/g due to its indigestibility.
• Soluble Fiber: Fermented by gut bacteria; provides 0.5-3 kcal/g.
• Sugar Alcohols: Range from 0 kcal/g (erythritol) to 3 kcal/g (hydrogenated starch hydrolysates).
• Ethanol: Yields about 7 kcal/g and provides energy not accounted for by macronutrient-focused calculations.

These substances contribute to your overall energy intake, but they are not considered in the standard Atwater General Factors.

What About The Nutrition Label?

Food labels show calorie counts based on the reported energy content of the foods and beverages you consume, rather than just the macronutrient composition. This approach results in more accurate calorie counts. Here’s why:

Summary

• Reported Energy Content: Reflects a more accurate calorie count by considering various factors.
• 4-4-9 Method: A generalized approach that might not capture all variables affecting calorie content.
• Other Calculations: Consider specific factors and variations in fibers and sugar alcohols, yielding more precise results.

So, while your calorie intake and macronutrient intake might not always “add up” neatly, this typically indicates a more accurate reflection of the actual energy content of the foods you consume, not a miscalculation.

Note

Calorie labels often round numbers for simplicity. For example, a product may list 150 calories instead of 148.5 or 152.7. Some people believe you should calculate calorie intake based on macronutrients to get a more precise number. However, this logic is flawed because macronutrient values are also rounded.

Key Points:

• Calorie Labels: Often rounded for simplicity (e.g., listed as 150 instead of 148.5 or 152.7).
• Macronutrient Labels: Also subject to rounding errors.
• Conclusion: Calculating calories from macronutrients just replaces one rounding error (calorie count) with another (macronutrient count). This doesn’t result in more precise calorie counts.

Conclusion: Why bother?

Setting Macro Guidelines and Calorie Expectations

Establishing general macronutrient guidelines based on your overall calorie limit is a sensible approach. Nutrition apps and coaches favor using macro targets because they offer an easy and clear method to communicate dietary goals. As long as you approximate your macro targets and maintain consistent intake of substances like ethanol, sugar alcohols, and fiber, your total daily intake of metabolizable energy should remain relatively stable. However, don’t expect your macronutrient intake and calorie intake to align perfectly.

Key Points:

• Macro Guidelines: Setting them based on total calorie limits is practical.
• Simplicity: Apps and coaches use macro targets for clear, concise communication.
• Consistency: Maintain steady intake of ethanol, sugar alcohols, and fiber for stable energy intake.
• Expectation: Calorie intake and macronutrient intake won’t always match perfectly.