Tiny Broccoli

Portion Control: Pop Sensation or Real Solution?

Portion PerfectionIf you’re looking for a hot concept in weight management and food policy, portion control is a good pick. But what are the distinctions between misleading hype and real scientific outcomes. Few scientists have studied this question as thoroughly as Barbara Rolls. So it was a rare privilege at the WM DPG Symposium to have Rolls take us on a tour of the evidence.

In the course of her presentation, she made five very helpful observations grounded by evidence.

  1. Big portions = big intake. Randomized, controlled trials provide good evidence that, in the short term, people eat more when they’re offered bigger portions.
  2. Importance of portions for causing obesity remains unproven. Evidence for the long-term effects of large portions is rather limited. Epidemiological associations are not sufficient for proving causality.
  3. Single meal studies can’t be extrapolated to sustainable effects. Rolls cautioned that many short-term effects wear out in the long term, especially when the effect depends upon perception and not physiology.
  4. Aspirational regulatory solutions need good evidence. Efforts to cap portion sizes, as was attempted in New York, are quite challenging to implement without compelling data to back them up.
  5. Portion size and energy density both need attention. Simply manipulating portion size without regard to energy density tends not to have sustainable benefits. Working with both variables can exert better, more sustainable effects.

Rolls has created an impressive body of evidence on portion size and its role in obesity. But she’s remarkably disciplined about identifying what’s actually known to work. Presumptions are no substitute for real knowledge.

Close enough is not good enough for dealing with a counter-intuitive, chronic disease like obesity.

Click here and here for more on the subject.

Tiny Broccoli, photograph © Stephanie Kilgast / flickr

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April 17, 2016