Diet drinks or foods may actually promote weight gain and
trigger diabetes because the brain misreads the number of calories present and
reduces metabolism, a new study suggests.
Researchers at Yale University in the US discovered that the
body stops burning energy from food if there is a ‘mismatch’ between food
sweetness and calories.
In nature, sweetness signals energy and the greater the
sweetness the more calories are available, so the brain has evolved to expect
the two to come together. When they do not, the brain can become confused,
thinking there are fewer calories to burn.
This research should be enough to convince you that
artificial ingredients, whether they be in food or drink, can screw up your
system
The scientists say it could help explain previous studies
that have suggested that artificial sweeteners can increase blood sugar levels
and possibly trigger diabetes.
“A calorie is not a calorie,” said senior author Dana Small,
Professor of Psychiatry at Yale University School of Medicine.
“The assumption that more calories trigger greater metabolic
and brain response is wrong. Calories are only half of the equation; sweet
taste perception is the other half.
“Our bodies evolved to efficiently use the energy sources
available in nature. Our modern food environment is characterized by energy
sources our bodies have never seen before.
“When sweet taste and energy are not matched less energy is
metabolized and weaker, or inaccurate, signals are sent to the brain. Either one of these effects may affect
metabolic health.”
For the new study, scientists scanned the brains of 15
people when they were drinking diet drinks, and compared them to regular
beverages. They also monitored how much energy was burned by the body.
They found when there was a ‘mismatch’ between sweetness and
calories - as is often the case with diet drinks or foods because they are not
as sugary - the calories fail to trigger the body’s metabolism. Reward circuits
in the brain also did not register that calories had been consumed, which could
lead to eating more.
Commenting on the paper, Dominic Dwyer, Professor of
Psychology at Cardiff University, said:
“What the paper does imply, correctly
in my view, is that mismatches between calories and sweetness interfere with
metabolism of calories in a way that could have negative impact on weight gain,
diabetes, heart disease etc. but that determining the link between the
unprocessed calories and metabolic health needs future work.
“The most important implication is namely the fate of
calories consumed in the mismatch conditions.
“These are not efficiently metabolised at the time of
ingestion and thus processed later and/or stored either of which could drive
weight gain and interfere with metabolism.”
Tam Fry, of the National Obesity Forum, added: "This
research should be enough to convince you that artificial ingredients, whether
they be in food or drink, can screw up your system even though they may sound
healthy.
"They may be free of calories but not of consequences
and diabetes is only one of them. "
However other British experts were more skeptical about the
findings and warned people to stick to drinking water if they were concerned
about artificially sweetened drinks.
Naveed Sattar, Professor of Metabolic Medicine at Glasgow University,
said: “There is currently no strong evidence that diet drinks are necessarily
bad for you whereas there is stronger and consistent evidence for sugar
sweetened drinks being linked to higher diabetes risk.
“Overall, my advice to people drinking sugar-rich drinks
would be to replace with water but that if this is not possible, diet drinks
are still a better choice to prevent tooth decay.
“Whether diet drinks also help weight loss or other benefits
is uncertain and requires proper long term trials which are currently lacking.”
Tom Sanders, Professor emeritus of Nutrition and Dietetics,
at King's College London, added: “The statement that a calorie is not a calorie
is gobbledegook. Calories are a measure of the energy value of food. The remark
is as stupid as saying a pound of feathers is lighter than a pound of lead.
“The claim is not supported by the observational evidence on
people who are long-term consumers of artificial sweeteners.
“Furthermore, an analysis of trials of replacing sugar
sweetened drinks with artificially flavoured drinks show that there is some
weight loss. Weight gain is certainly is not caused by drinking artificial
sweeteners.”
The research was published in the journal Current Biology.
