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Humans On A Cafeteria Diet

In the 1970s, equally the modern obesity epidemic was exactly getting started, investigators were searching for novel brute models of diet-induced obesity.  They tried all sorts of things, from refined saccharify to diverse types of fats, but none of them caused obesity equally speedily in addition to reproducibly equally desired*.  1976, Anthony Sclafani tried something new, in addition to disarmingly simple, which he called the "supermarket diet": he gave his rats access to a diversity of palatable human foods, inwards add-on to criterion rodent chow.  They at ane time ignored the chow, instead gorging on the palatable nutrient in addition to speedily becoming obese (1).  Later renamed the "cafeteria diet", it remains the most rapid in addition to effective means of producing dietary obesity in addition to metabolic syndrome inwards rodents using company nutrient (2).


H5N1 few weeks ago, I was paging through doctor David Kessler's volume The End of Overeating, when I came across a citation for a newspaper with an extraordinary title: "Spontaneous Overfeeding with a 'Cafeteria Diet' inwards Men: Effects on 24-hour Energy Expenditure in addition to Substrate Oxidation."  Further interrogation revealed 2 to a greater extent than related papers, all from the interrogation grouping of doctor Eric Ravussin, who has dome about fantabulous operate on liberate energy balance, fat/carbohydrate/protein oxidation, in addition to obesity (e.g, 3). 

The foremost written report was published inwards 1992 (4), in addition to seems initially to receive got exactly been an evidence to pattern a novel means of accurately measure nutrient intake inwards free-living humans, which is notoriously difficult.  Investigators created an "automated food-selection system" consisting of 2 large vending machines filled with a diversity of prepared foods of known calorie in addition to nutrient compositions.  They recruited 10 lean, salubrious men.  At the showtime of the experiment, the investigators took iv days to decide each volunteer's liberate energy requirement for weight maintenance.  Then, inwards the setting of a metabolic ward where no other nutrient was available, the volunteers were allowed to select in addition to eat equally much nutrient equally they pleased from the vending machines over 7 days.  The foods available included English linguistic communication muffins, French toast, pancakes with syrup, scrambled eggs, chicken pie, cheeseburgers, margarine, white sugar, diverse cakes in addition to puddings, apples, jelly beans, Doritos, one thousand in addition to M's, apple tree juice, 2% milk, sodas in addition to several other foods.

I dubiety the investigators were prepared for what they observed when they turned the 10 men loose on those vending machines.  They at ane time began consuming excessive calories, an average of 1,544 kcal per twenty-four hr menses inwards excess of their previously determined liberate energy needs (with a fairly typical macronutrient composition past times percentage).  That amounts to a roughly 60% increment inwards calorie intake over baseline, a striking change, peculiarly since it was completely voluntary.  Over the course of pedagogy of 7 days, the volunteers gained an average of 5.1 lb (2.3 kg). 

The adjacent 2 studies used a similar pattern in addition to were both published inwards 1995.  One notable departure is that they were conducted inwards virile soul in addition to woman soul Pima Indians, a population with a high susceptibility to obesity upon adopting an industrial diet/lifestyle.  Another departure is that these studies were conducted with a larger number of volunteers of diverse degrees of fatness.

The adjacent study, whose championship I mentioned above, was inwards Pima men (5).  After determining the volunteers' liberate energy needs for weight maintenance, they laid them loose on vending machines total of "familiar, palatable foods."  Over the course of pedagogy of the adjacent 5 days, they consumed an excess of 1,637 kcal per day, a 56% increment over baseline.  33 volunteers out of 34 overate relative to baseline, including both lean in addition to obese individuals, resulting inwards an average weight gain of 2 lbs (0.9 kg). 

The tertiary in addition to lastly written report was inwards Pima women (6).  The pattern of this written report was essentially the same equally above.  The women overate past times an average of 27% in addition to gained 0.9 lbs (0.4 kg) over 5 days. The obese women consumed to a greater extent than calories, proportionally to a greater extent than fat, in addition to gained to a greater extent than than twice equally much trunk fatty equally the lean women.


Main Points

There are a few interesting things that tin live gleaned from these studies:
  1. Just equally inwards rats, exposing humans to a diversity of readily accessible, liberate energy dense, palatable foods causes excessive nutrient intake in addition to rapid weight gain.  The grade of overeating varies past times individual, but nearly everyone overeats to about degree.  Whatever the mechanism(s) underlying this may be, the phenomenon has of import implications for the commercialization of nutrient in addition to the associated obesity epidemic inwards affluent nations.
  2. In most cases, changes inwards trunk fatness are primarily, but non exclusively, the termination of changes inwards liberate energy intake. This is a consistent finding across many studies.  The obesity epidemic inwards the USA has corresponded with a large increment inwards daily calorie intake, in addition to also a substantial increment inwards liberate energy expenditure, because larger bodies hand notice to a greater extent than energy.  Thus, liberate energy "flux" has increased past times roughly 400 kcal/day inwards the USA since the 1970s (3).  
  3. When liberate energy intake is increased, liberate energy expenditure also speedily increases, although over the fourth dimension scale of these studies it was non nearly sufficient to residual out the extra liberate energy intake.
  4. When a diet of mixed macronutrient composition is eaten to excess, the saccharide is preferentially burned off, field the fatty is generally shunted into fatty tissue.  This makes sense, because why would the trunk larn through the inefficient procedure of converting saccharide to fatty for storage when it tin exactly shunt dietary fatty straight into fatty tissue?  This does non imply that dietary fatty is fattening nether atmospheric condition of liberate energy balance. 
  5. Under the atmospheric condition of the experiment, obese Pima women spontaneously ate to a greater extent than calories in addition to selected nutrient with a higher fatty in addition to lower saccharide content than lean Pima women.  They also gained to a greater extent than than twice equally much fatty volume on average, mayhap pointing to differences underlying obesity susceptibility betwixt individuals.  I believe this is similar to other observational findings on the subject.  

*High fatty diets, peculiarly inwards combination with refined starches in addition to sugars, were alongside the most effective.  The composition of these diets has been refined since then, in addition to modern "purified" high-fat diets reliably get obesity inwards susceptible strains of rodents.  The most usually used diet is Research Diets D12492, which is 60% fatty past times calories, in addition to composed generally of lard, soybean oil, casein, maltodextrin, sucrose in addition to cellulose (7).  It tastes form of similar raw cookie dough, in addition to the rats are crazy virtually it.
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