Why artificial sweeteners can actually increase calorie consumption
Brain’s reward centres may recalibrate ratio of energy to sweetness when diet contains artificial sweeteners for prolonged period. Also in health news: redhead genes linked to melanoma risk
Foods with artificial sweeteners are often seen as a dieter’s alternative to sugar, but a new study has identified how artificial sweeteners can actually stimulate appetite and make you eat more. In tests on fruit flies and mice, researchers in Sydney have found a complex network in the brain that responds to artificially sweetened food by telling the animal it hasn’t eaten enough energy. The animals, which were exposed to a diet containing artificial sweetener for prolonged periods (more than five days), were found to consume significantly more calories when they were then given naturally sweetened food.
“Through systematic investigation of this effect, we found that inside the brain’s reward centres, sweet sensation is integrated with energy content. When sweetness versus energy is out of balance for a period of time, the brain recalibrates and increases total calories consumed,” says lead researcher Associate Professor Greg Neely from the University of Sydney’s Faculty of Science. “When we investigated why animals were eating more even though they had enough calories, we found that chronic consumption of this artificial sweetener actually increases the sweet intensity of real nutritive sugar, and this then increases the animal’s overall motivation to eat more food.”
The researchers also found artificial sweeteners promoted hyperactivity, insomnia and decreased sleep quality – behaviours consistent with a mild starvation or fasting state – with similar effects on sleep also previously reported in human studies. The study appears in the journal Cell Metabolism.
Red hair gene variation drives up skin cancer mutations
Gene variants associated with red hair, pale skin and freckles are linked to a higher number of genetic mutations in skin cancers – an effect comparable to an extra 21 years of sun exposure in people without these genetic variants – according to researchers at the Wellcome Trust Sanger Institute and University of Leeds.
Red-headed people, who make up between 1 and 2 per cent of the world’s population, have two copies of a variant of the MC1R gene which affects the type of melanin pigment they produce, leading to red hair, freckles, pale skin and a strong tendency to burn in the sun. The research, published in Nature Communications, showed that even a single copy of the MC1R gene variant increased the number of mutations in melanoma skin cancer, the most serious form of skin cancer. Many people without red hair carry these common variants, the researchers say.
“This important research explains why red-haired people have to be so careful about covering up in strong sun. It also underlines that it isn’t just people with red hair who need to protect themselves from too much sun,” says Dr Julie Sharp, head of health and patient information at Cancer Research UK. “People who tend to burn rather than tan, or who have fair skin, hair or eyes, or who have freckles or moles are also at higher risk.
“For all of us the best way to protect skin when the sun is strong is to spend time in the shade between 11am and 3pm, and to cover up with a T-shirt, hat and sunglasses. And sunscreen helps protect the parts you can’t cover; use one with at least SPF15 and 4 or more stars, put on plenty and reapply regularly.”
Water intake overlooked in obese individuals
The potential secret weapon in the battle against obesity is actually already a simple part of our diets: water. People who are obese and have a higher body mass index (BMI) are more likely to be inadequately hydrated and vice versa, suggests new research from the University of Michigan published in the Annals of Family Medicine.
Although the link between hydration and weight requires further probing, hydration has lately been considered a cornerstone of a weight-loss diet, notes lead author Dr Tammy Chang, an assistant professor in the university’s department of family medicine. “We often hear recommendations that drinking water is a way to avoid overeating because you may be thirsty rather than hungry,” she says.
Chang and colleagues looked at a nationally representative sample of 9,528 adults in the US. Roughly a third of the adults, who spanned ages 18 to 64, were inadequately hydrated. The study suggests that people with higher BMIs – who are expected to have higher water needs – might also demonstrate behaviours that lead to inadequate hydration.
The authors note the findings do not indicate that inadequate hydration causes obesity or the other way around, but highlight an important relationship between the two. Chang says eating healthy foods high in water content, such as fruits and vegetables, can improve hydration status, though more studies are needed to know whether hydration status can influence weight.