Written by Tana Amen, BSN, RN on Monday, 15 April 2013. Tana’s BlogNutrition

One of the most ancient healing foods, olive oil was so prized by the ancient Greeks that Homer called it “liquid gold.” Study after study has uncovered a treasure trove of health benefits, from quelling inflammation to protecting against heart disease and even cancer.

Not only is extra virgin olive oil (EVOO) rich in disease-fighting antioxidants, but even smelling its aroma has surprising weight-control benefits, according to a new study by German scientists.

The researchers found that compared to other types of fats, EVOO is the most beneficial for warding off extra pounds. Meals that include EVOO are more likely to leave people feeling pleasantly full than those that include comparable amounts of butter, lard, or rapeseed oil.

Participants were randomly divided in 5 groups. They weren’t told which fat they would be eating. One group received food supplemented with EVOO and others were given food that contained lard, butter, or rapeseed oil. Each group was told to eat this food daily, in addition to their usual diet. A control group received fat-free food. Participants were tracked for three months.

The group who ate EVOO showed the greatest increases in serotonin, a feel-good brain chemical linked to satiety and reported finding the food very filling. And despite being given extra food, they adapted their eating habits–and none of them gained any weight. Conversely, the groups who ate food with lard or rapeseed oil packed on extra pounds.

The control group had the lowest level of serotonin in their blood. Basically, they weren’t satisfied by the fat-free food, remained hungry, and therefore overate, leading to weight gain.

This finding mirrors a frightening trend I discuss in my new book, The Omni Diet: The Revolutionary 70% Plant + 30% Percent Protein to Lose Weight, Reverse Disease, Fight Inflammation, and Change Your Life Forevernow available.

In the US, where obesity rates have more than doubled since the 1980s, the decade in which our national fat-free craze started to take off. As the book explains, that’s not a coincidence. Ironically, as the public began gobbling up everything from fat-free cheese to fat-free cookies, Americans started getting fatter instead of thinner.

Currently, nearly 36 percent of Americans are obese–and the rate is expected to skyrocket to 44 percent by 2030 if current trends continue. The dirty little secret I expose is that to make fat-free food palatable, manufacturers have added huge amounts of sugar, fillers, and chemicals that leave people feeling so unsatisfied that they overeat. Indeed, many fat-free foods contain up to 30 percent more calories than the full-fat versions.

In the study, the researchers decided to explore why “liquid gold” was more effective at curbing appetite than the other fats studied. “The findings surprised us because rapeseed oil and olive oil contain similar fatty acids,” study author Professor Peter Schieberle reported in a statement issued by Technical University of Munich.

To solve this mystery, the scientists analyzed the effects of two aroma compounds found in EVOO. In a second phase of the study, participants were divided into two groups. One group ate food flavored with olive oil aroma extracts, while the control group ate plain fat-free food.

The results revealed the remarkable role that aroma plays in weight control. Food with the aroma compounds stimulated the participants’ brains to produce more serotonin, and they felt satisfied, while the control group wolfed down an extra 176 kilocalories a day.

The scientists report that olive oil aroma compounds appear to slow down the rate at which liver cells absorb sugar in the blood. The faster blood sugar from food is absorbed, the sooner a person is likely to feel hungry again, explaining why it’s so easy to pig out on sugary foods like donuts.

These intriguing results may help explain why slowly absorbed foods, such as fresh organic greens drizzled with fragrant EVOO, keep our brains happy and our bellies pleasantly full, without fear of weight gain.