In previous installments, we've proven the following: A calorie is not a calorie when you eat it at a different time of day.
A calorie is not a calorie when you eat it in a differently processed form.
A calorie is not a calorie when you eat it as a wholly different food.
A calorie is not a calorie when you eat it as protein, instead of carbohydrate or fat.
A calorie is not a calorie when you change the type of fat, or when you substitute it for sugar.
Controlled weight-loss studies do not produce results consistent with "calorie math".
Even if all calories were equal (and we've proven they're not), the errors in estimating our true "calorie" intake exceed the changes calculated by the 3500-calorie rule ("calorie math") by approximately two orders of magnitude.
(This is a multi-part series. Return to Part I, Part II, Part III, Part IV, Part V, or Part VI.)
Empirical Evidence: A Calorie Is Not A Calorie When You Add Carbohydrate To A Zero-Carb Diet
There are many anecdotal reports of people finding it difficult or impossible to gain weight on a zero-carb diet, even with massive overfeeding. Yet there are controlled trials that seem to show high-fat diets having no such overfeeding advantage. Why not?
This study provides some clues: J Nutr Biochem. 2003 Jan;14(1):32-9.
Effects of dietary carbohydrate on the development of obesity in heterozygous Zucker rats.
Morris KL, Namey TC, Zemel MB.
"...We fed 6-week old male heterozygous (fa/+) lean rats carbohydrate-free diets containing primarily saturated fat either ad libitum or pair-fed. These diets were compared to standard chow and to a high saturated fat mixed diet containing 10% energy from sucrose for 4 weeks." This is a good start: many "high-fat" diet trials use industrial lard containing ~20% linoleic acid (an omega-6 fat), or industrial seed oils with even greater LA content - which, as we've seen in the previous installment, is strongly implicated in the development of obesity. Furthermore, most "high-fat" laboratory diets contain about 20% purified sugar...which, as we've previously noted, seems to be obesogenic by itself. A Short Digression: "High-Fat" Almost Always Means High Sugar
The results of Morris 2003 call into question all obesity research featuring "high-fat diets". First, they're usually on a strain of mice (C57BL/6, or "black six") specifically selected for its propensity to quickly become obese when fed high-fat diets, unlike other strains of mice (let alone other animals, like humans, that aren't natural seed-eating herbivores). More importantly, in nearly every case, they use D12492 - a mix of purified ingredients containing no actual food, and specifically designed to make C57BL/6 mice obese as quickly as possible. (More here, via Dr. Chris Masterjohn)
D12492 contains 20% purified sugars.
So be skeptical whenever you see a headline claiming negative effects for "high-fat diets". All diets were standardized to 20% protein and 11% corn oil. (Yes, these are industrial Frankendiets.) The carbohydrate-free diet contained 69% coconut oil; the 10% sucrose diet contained 59% coconut oil and 10% sucrose (table sugar), with no other carbohydrate; and the "standard chow" diet contained 59% cornstarch and no coconut oil.
Does that matter? 10% carbohydrate is still VLC, right? That's only 50 carbs on a 2000-calorie diet...and it's still almost 60% coconut oil, so they should be mostly in ketosis, right?
Here's what happened after four weeks. First, the food intake figures, from Table 2:
The zero-carb rats ate 36% more "calories" than the chow rats, and about the same (3% more) as the 10% sucrose rats...and the pair-fed zero-carb rats ate the same number of "calories" as the 70% carb ("standard chow") rats. (That's what "pair-fed" means: one group is fed only as much as another group eats.) So if the CICO zealots are correct (IT'S PHYSICS!!!1!!1), the standard chow and pair-fed rats ought to be lean, while the zero-carb and 10% carb rats ought to be obese ( via gnolls.org ).