Reduced-fat food products are gaining in popularity. More
and more people are choosing “light” products in an attempt to lose weight, or
at least in the hope that they will not gain any pounds. But whether these
products are effective or not is a matter of dispute: While it is true that
they contain fewer kilojoules, people tend to overcompensate by eating more if
they do not feel full.
Now a study has shown how “natural” oils and fats regulate
the sensation of feeling full after eating, with olive oil leading the way. So
what makes this oil so effective?
How the study was
Work groups at Technische Universität München (TUM) under
Professor Peter Schieberle and at the University of Vienna under Professor
Veronika Somoza studied four different edible fats and oils: Lard, butterfat,
rapeseed oil and olive oil.
Over a period of three months, the study participants ate
500 grams of low-fat yoghurt enriched with one of the four fats or oils every
day – as a supplement to their normal diet.
“Olive oil had the biggest satiety effect,” reports Prof.
Peter Schieberle, Head of the TUM Chair of Food Chemistry and Director of the
German Research Center for Food Chemistry. “The olive oil group showed a higher
concentration of the satiety hormone serotonin in their blood. Subjectively
speaking, these participants also reported that they found the olive oil
yoghurt very filling.” During the study period, no member of this group
recorded an increase in their body fat percentage or their weight.
Aroma is the key
“The findings surprised us,” admits Schieberle, “because
rapeseed oil and olive oil contain similar fatty acids.” The researchers
decided to turn their attention to a completely different type of substance –
the aroma compounds in olive oil. In the second part of the study, one group
was given yoghurt with olive oil aroma extracts and a control group was given
The results were conclusive: The olive oil group’s calorie
intake remained the same, but the control group had been consuming an extra 176
kilocalories per day. Schieberle explains: “The aroma group adapted their
eating habits – but the control group participants were obviously not able to
do likewise. We also found that in comparison to the other group, the control
group had less of the satiety hormone serotonin in their blood.”
Direct impact on
blood sugar level
How long the feeling of satiety lasts after eating depends
on a number of factors, but blood sugar level is particularly significant. The
faster it falls, that is to say, the faster the somatic cells absorb glucose
from the blood, the sooner the person will start to feel hungry again. In the
next part of their study, the researchers investigated which of the aroma
substances present in the oil are most effective at inhibiting glucose
The researchers used olive oils from Spain, Greece, Italy
and Australia for their study. The research team managed to identify two
substances that reduce the absorption of glucose from the blood in liver cells:
Hexanal and E2-Hexenal. They also discovered that Italian olive oil contained
larger amounts of the two aroma compounds.
“Our findings show that aroma is capable of regulating
satiety,” concludes Schieberle. “We hope that this work will pave the way for
the development of more effective reduced-fat food products that are