Monday, September 12, 2005

Examining Low-Carb & Low-Fat Diets

Part 1: Macronutrient intake as a percentage of calories: A useless measure of diet quality

For years a number of policy makers, agencies and health organizations have established that a "balanced diet" is one that provides no more than 30% of total calories from fat, 55-65% of calories from carbohydrate and 10-15% of calories from protein - regardless of caloric intake. Few challenge the notion that as calories increase or decrease, these macronutrient ratios remain the same; even fewer have taken the time to consider the detrimental effects of ignoring nutrient-density and instead stay focused on macronutrient mix.

Let me state it here, the overall macronutrient mix - that is the percentage of calories each day you consume as carbohydrate, fat and protein - is not a measure of diet quality.

Never has been, never will be.

But few will tell you that straight out and will instead parrot the party-line to have you try to maintain your calorie intake by the useless formula. Even though, at the end of the day, the percentage of your calories from each macronutrient is a moot point - your nutrient-density for essential micronutrients is the key determinant of diet quality.

Always has been, always will be.

Believe it or not, as a nation, we do come close to the ideal ratios - as CDC Data on average macronutrient intake as a percentage of calories each day shows, on average we consume (average men and women):
  • 32.8% fat, 15.3% protein and 50.3% carbohydrate.

This is a change from our intake from 1971 when we consumed (average men and women):

  • 36.5% fat, 16.5% protein and 43.9% carbohydrate.

So why are we so fat?

The experts will tell us that while we've improved our macronutrient percentages, we've also increased our intake of calories and that is the problem - men are eating approximately 168 more calories and women 335 more calories. The old "it's the calories stupid" answer.

Which begs the question - why are we eating more calories?

There are a number of reasons put forth - larger portion sizes, easy access to fast food, more convenience food available, eating out more often, liquid calories, yo-yo dieting, lack of willpower, sedentary lifestyles, heck even fewer sidewalks built in new suburban neighborhoods.

Few are asking the important question - did a modification of our macronutrient intake have an unintended consequence on our satiety level and ability to control food intake, and thus calorie intake?

Research investigating the metabolic effects of low-carb and controlled-carb nutritional approaches reveals that when macronutrient mix is modified to restrict carbohydrate and increase protein and fat (as a percentage of calories) an interesting thing happens in the metabolism - high satiety levels with a spontaneous calorie reduction without counting calories!

Yet, the "experts" continue to caution that low-carb diets are potentially unhealthy and no better than calorie-restricted or low-fat approaches; that in the long-term you're better off following a diet that maintains that 30:15:55 ideal formula so you can continue with it once you've lost the weight.

The strongest caution cited is that low-carb diets encourage eating high amounts of fat - about 60% of calories each day while one is losing weight!

Good grief that sounds high, doesn't it?

But...if someone is eating 2600 calories a day today, while they're overweight, just what does a very low-carb diet do to their fat intake if they reduce calories to 1600 each day? Surprisingly, very little. In fact, their intake of fat would increase just 10g - or about 2 teaspoons of olive oil. why are we being told that to follow a low-carb diet means you have to substantially increase your intake of fat?

I don't know why - but if you actually start looking at the numbers, NOT the percentage of calories each day, the real increase is in protein, not fat.

And the evidence suggests that more protein in the diet actually is the driving force for greater satiety and the "metabolic advantage" to burn more calories. This increase in protein is in stark contrast to the protein intake on a calorie-restricted, low-fat diet that insists macronutrient intakes must remain at 30:15:55, causing a significant decrease in protein intake when followed according to the percentages!

Don't believe me, have a look for yourself:

  • 2600 calories per day @ standard American intake percentages
    52% carbohydrate = 1352 calories = 338g
    15% protein = 390 calories = 97g
    33% fat = 858 calories = 96g
  • 1600 calories per day very low-carb weight loss percentages
    5% carbohydrate = 80 calories = 20g
    35% protein = 560 calories = 140g
    60% fat = 960 calories = 106g
  • 1600 calories per day recommended low-fat weight loss percentages
    55% carbohydrate = 880 calories = 220g
    15% protein = 240 calories = 60g
    30% fat = 480 calories = 53g

As you can see, on a very low-carb approach, there is NOT a significant increase in how much fat is eaten, even though the percentage of calories from fat significantly increases.

However, on a calorie-restricted, low-fat approach, protein intake as a percentage is the same, but intake by the gram significantly decreases! In fact, it's a 39% decrease in protein intake which is a direct 39% decrease in amino acid intake.

Not only that, but due to the restriction on fat intake - limited to 30% of calories - the quality of protein sources are significantly impacted as one tries to maintain the fat restriction and is forced to limit quality protein sources that also are higher in fat content, like nuts and eggs.

The data available shows that controlled-carb approaches - from Atkins to the Zone - offer a much greater intake of essential nutrients - amino acids, fatty acids and vitamins & minerals - when compared with traditional low-fat approaches.

At the end of the day what matters most is essential nutrients not what percentage of your diet was fat or protein or carbohydrate. Tomorrow I'll compare, side-by-side, a 1600-calorie very low-carb menu with a 1600-calorie low-fat menu and detail what each provides nutritionally at the end of the day. It will be an eye-opener!


  1. Thanks for visiting my blog and leaving a comment. I actually meant to link to you weeks ago, and tonight I got it done.

  2. Anonymous8:56 AM

    Waiting for my eyes to be opened!