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Eat good fats, be satiated – more from the NEJM

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Nov 17

Last week we commented on an editorial that appeared in the NEJM and promised to follow up on an original article that appeared in the same issue. Today we’ll talk about this study that might validate the feelings of anyone who has dieted and who has thought that they were doomed to regain the weight that they had lost. Let’s take a look.

What did they do? The investigators recruited 50 individuals who were overweight or obese to participate in a 10-week weight loss program. The weight loss program consisted of a very low calorie diet (Optifast + 2 cups of low-starch vegetables). At the beginning of the trial (baseline), at the end of the 10-week program, and 1 year later, the investigators assessed participants’ subjective ratings of appetite and levels of various hormones and enzymes (leptin, ghrelin, peptide YY, inhibitory polypeptide, GLP1, amylin, pancreatic polypeptide, CCK, and insulin).

What did they find? First, of the 50 participants who enrolled in the study, 4 dropped out during the 10-week weight loss program. Another 7 participants did not lose at least 10% of their body weight and were not included in the 1-year follow-up. Five of the remaining 39 participants who started the 1-year follow-up dropped out of the study during that time. So, 34 of the original 50 participants (68%) completed the study.

Second, for the 34 participants who completed the study, they lost weight (an average of 13.5 kg or almost 30 lbs) during the 10-week program  and regained some of that weight (an average of 5.5 kg or almost 12 lbs) during the 1-year follow-up.

Third, for the 34 participants who lost at least 10% bodyweight during the 10-week program and completed the study, subjective ratings of hunger and desire to eat were greater following weight loss (at week 10 and 1 year later) as compared to at baseline. Interestingly, levels of ghrelin were increased at week 10 (after weight loss). Ghrelin levels decreased from week 10 to the 1-year follow-up, but remained higher than they were at baseline. Conversely, levels of leptin were decreased at week 10 (after weight loss). Leptin levels increased from week 10 to the 1-year follow-up, but remained lower than they were at baseline. Why is this interesting or important?

What do we make of this? Remember that ghrelin is a hormone produced by the stomach and pancreas that stimulates hunger, whereas leptin is a hormone produced by adipocytes (fat cells) that promotes satiety. You might think of these two hormones as the gas and the brake of our body’s signals to eat. Under conditions of fasting, levels of ghrelin are increased (to stimulate hunger) and levels of leptin are decreased (to reduce satiety), which seems to make sense if one is at risk of starvation and should be eating. What is interesting about this paper (and perhaps why it was accepted into such a prestigious journal) is that the investigators have shown that these changes persist for up to a year after a 10-week very low calorie diet program. Or, do they?

An alternative explanation? At the end of the 10-week diet program, the methods section states that, “participants received individual counseling and written advice from a dietician on a dietary intake that would be consistent with their calculated energy expenditure, with the aim of weight maintenance. No specific macronutrient ratios were prescribed, but carbohydrates with a low glycemic index and a reduced intake of fat were recommended.” Ah ha, so not only was the 10-week diet very low in fat, but a reduced intake of fat was recommended for the 1-year follow up period as well (side note: we recommend skepticism surrounding any acute intervention in adults that it purported to have effects that persist for a year).

So, why might the low-fat recommendation be important? Well, studies have shown, “that the direct exposure of receptors in the oral cavity and small intestine to fat, specifically fatty acids (FAs), induces potent effects on gastrointestinal (GI) motility and gut peptide secretion that favor the suppression of appetite and energy intake.” In addition, other studies have shown that, “deletion of the genes encoding ghrelin and/or its receptor prevents high-fat diet from inducing obesity.” Together, these data suggest that eating fatty acids in the presence of a low ghrelin environment reduces appetite, energy intake, and weight gain. And guess what? Obese individuals tend to have lower levels of ghrelin as compared to non-obese individuals. So, perhaps the recommendation for reduced intake of fat in this study both in the 10-week program and during the 1-year follow-up promoted the increases in ghrelin, increases in appetite, and the re-gaining of weight.

In fact, if you compare the results of this study to others in which participants were instructed to consume a healthy fat like coconut oil, there is a stark difference in that consumption of coconut oil (but not soybean oil) resulted in reductions in energy intake, carbohydrate consumption, waist circumference, BMI and positive changes in blood lipids.

So, if you want to lose weight and have a good blood lipid profile, consume healthy fats. You’ll feel good and your body will thank you for it.

Have a great weekend!

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