To millions of Americans who diet hard every year and never seem to lose a gram, this is going to be an incredibly obvious statement, but the fact that it’s coming from a group of research scientists and not “just” a certified nutritionist might make all the difference:
Every person metabolizes food differently, which means there is no one “correct” diet for losing weight.
That’s the conclusion that a massive study from the Weizmann Institute of Science in Israel came to in the 11/19/2015 issue of the journal Cell. According to the study, the existing methods of assigning ‘danger levels’ to meals — primarily, ‘how many carbs does it have?’ and ‘what is its glycemic index/glycemic load?’ — are more or less complete failures on the scientific level.
“Ascribing a single PPGR [blood glucose response] to each food assumes that the response is solely an intrinsic property of the consumed food. However, the few…studies that examined interpersonal differences in PPGRs found high variability in the response of different people to the same food,” the study reads.
In other words, your body might simply be responding to a factor in your food other than its carb count or glycemic load. In fact, there are a number of factors that can significantly change how a given person’s body responds to a specific meal, according to the study. They include:
- Genetics,
- Lifestyle,
- Insulin sensitivity,
- Exocrine pancreatic and glucose transporter activity levels, and
- The specific species (and amounts) of bacteria living in your intestinal tract.
There’s No Safe Food
It’s important to note that one of the findings of the study is that there is no food that is safe for all people. “When comparing the PPGRs of different people to the same meal, we found high interpersonal variability, with the PPGRs of every meal type (except fructose) spanning the entire range of PPGRs measured in our cohort.” (Emphasis ours.)
Translated into laypeople speak, what that means is that there was no single type of meal that didn’t end badly for at least one person in the study — but eating fructose in particular ended badly for everyone.
Now, this doesn’t mean that there aren’t averages, and you probably already more-or-less know them. “For example, the average PPGR to rice and potatoes was relatively high, whereas that for ice cream, beer, and dark chocolate was relatively low, in agreement with published data.” White carbs are bad (on average), carbs loaded into other not-carby stuff are not so bad (on average)…except that there’s no real way to know where on those averages you personally actually are. Just because the average person can nom ice cream more safely than they do rice doesn’t mean you follow that rule. (It is worth noting, however, that ‘more carbs equals more blood sugar’ as a general rule was true for 95.1% of all studied people, so your chances of being able to just wolf down linguini all you want are a little bit less than one in twenty. Sorry.)
Pre-Diabetes Is Real
The diagnosis of ‘prediabetes’ has only been a thing in the past decade or so, and many laypeople don’t regard it as a ‘real’ disease — but the study proves that it very much is. The threshold for a diagnosis of prediabetes is an A1C (90-day average blood sugar) around 5.7. The study found that an A1C of 5.5 or higher magnifies the effect every meal you eat has on your blood sugar. In other words, once your blood sugar gets high enough, it creates a self-enforcing cycle of increasing sugar.
Other Factors That Were Consistent
A few other factors showed up in every person studied. Blood sugar response was consistently lower if:
- A person had eaten an ample amount of dietary fiber 6-24 hours before the meal,
- A person had gotten an ample amount (8+ hours) of sleep the night before the meal,
- The meal contained a higher amount or proportion of fat to carbohydrates,
- The meal contained a higher proportion of water or alcohol than average, and
- The person’s gut flora had the ability to digest the kinds of carbs found in the meal.
That last one might well explain why so many Asian people can eat rice all day without adding pounds, and why so many Mediterranean people can nosh pasta at every meal and stay skinny, but so many Americans can’t do either one.
Hope for the Future
The study’s authors have grand ambitions: this study was the first step in establishing a standard “who should eat what” program. Their hope is to, someday soon, be able to take a blood sample, a stool sample, and a short questionnaire and combine them to discern precisely what you should and shouldn’t eat.
Until then, the rest of us will have to muddle along playing the odds — but at least now, if it doesn’t work out, we know it’s probably not our fault. It turns out, there really is no all-purpose effective diet for losing weight.
(Featured Image courtesy of CGP Grey via Flickr, shared using a Creative Commons 2.0 license.)
