Do all dietary fats increase body weight? The Olive oil case

Is it paradoxical that olive oil intake does not increase body weight? It seems so, as olive oil is an energy-dense food, frequently consumed in south European countries. These countries have increasingly high obesity prevalence, according to different international organizations, including the World Health Organization. Actually, in 2008 the New York Times published that the Mediterranean Diet had succumbed to fast food.

However, recent evidences are pointing out in the opposite direction, indicating that olive oil could be helpful against body weight gain. A cross-sectional study on 6,352 Spanish adults, published early this year, showed that olive oil intake did not affect body mass index (BMI) and the risk of obesity after adjustment for total energy intake.


Alright, but this is a cross-sectional study. ¿What happens if olive oil is administrated to a group of human subjects? The strongest evidence we have to date is the results of the PREDIMED study. This is a three-arm randomized trial aimed to assess the effects of Mediterranean Diet in primary cardiovascular prevention in more than 7000 individuals at high cardiovascular risk. A substudy of the PREDIMED trial showed that increased adherence to the Mediterranean Diet, with 1L per week of olive oil, was inversely associated with diabetes incidence, which occurred in the absence of significant changes in body weight or physical activity.

It has been even suggested that olive oil intake, as part of a Mediterranean Diet, is inversely associated with BMI and obesity in adults and children. Therefore, it might not be the excess of fat from olive oil intake what is causing the epidemic of obesity in Southern Europe, but as the New York Times suggested, but the retreat of the traditional diet of the region.

Obesity facilitates tumor growth in mice redardless of their diet

Epidemiologic studies have strongly associated the incidence of cancer with obesity, but their pathophysiologic connections remain obscure. Researchers at the Institute of Molecular Medicine at the University of Texas Health Science Center at Houston may have discovered a new explanation as to why obese patients with cancer often have a poorer prognosis compared with those who are lean.

Mikhail G. Kolonin and his colleagues evaluated how adipose stromal cells (ASC), transplanted  into mice, can serve as perivascular adipocyte progenitors that promote tumor growth. Their initial results confirmed this hypothesis: In obese and lean mice that ate the same diet, tumors grew much faster in obese mice than they did in lean mice. They also found that ASC were expanded into the circulation in obesity and that they traffic from endogenous adipose tissue to tumors in several mouse models of cancer.

Once in the tumors, some of these cells developed into fat cells, while others were incorporated into tumor-associated blood vessels, which support tumor growth by bringing in oxygen and nutrients to cancer cells. According to the researchers, this ability of ASC is likely one of the main reasons that the excess of these cells in tumors was associated with increased malignant cell proliferation.


Source: Cancer Research

Another way to measure obesity

Traditionally, Body Mass Index (BMI) has been used to measure obesity. Now, scientists propose a novel method that includes waist circumference (WC) in addition to BMI, providing better information about the risk of premature death for an individual. Known as A Body Shape Index (ABSI), the metric was tested on national health and nutrition data from 14,000 adults in the United States. This new parameter is based on WC adjusted for height and weight and was found to show a better correlation with death rate than does the BMI.

Death rates increased approximately exponentially with above average baseline ABSI, whereas elevated death rates were found for both high and low values of BMI and WC. The association of death rate with ABSI held even when adjusted for other known risk factors including smoking, diabetes, blood pressure, and serum cholesterol. ABSI correlation with mortality hazard held across the range of age, sex, and BMI, and for both white and black ethnicities (but not for Mexican ethnicity), and was not weakened by excluding deaths from the first 3 yr of follow-up.

Source: PloS ONE

Weight-loss drug obtains FDA approval

After 13 suspenseful years, the US Food and Drug Administration (FDA) has approved a pill that could help to fight the US obesity epidemic.

According to the FDA, Belviq (lorcaserin) can help people to lose about 3–4% of their body weight when combined with a healthy diet and exercise. The drug has been approved for use by obese people with a body mass index (BMI) greater than 30, and for a subset of overweight people (with a BMI of more than 27) who have health conditions such as high blood pressure, elevated cholesterol and type 2 diabetes.

The FDA had already rejected Arena’s first application for approval of Belviq in September 2010 because the compound seemed to produce tumours in rats and because the company could not statistically rule out an increase in the risk of heart-valve problems. Similar to fenfluramine, Belviq suppresses food cravings by mimicking the effects of serotonin in the brain, making people eat less and feel full. However, Belviq seems to activate only the serotonin 2C receptor in the brain, not the serotonin 2B receptor that is present in heart muscle.

The FDA’s turnaround this week came after Arena performed echocardiograms in nearly 8,000 people to measure heart-valve function, which revealed that there was no increase in heart-valve abnormalities among those taking the drug. The firm has agreed to run six post-marketing studies, including a long-term cardiovascular trial, and patients with congestive heart failure are advised not to take the drug.

Source: Nature (doi:10.1038/nature.2012.10923) http://www.nature.com/news/weight-loss-drug-wins-us-approval-1.10923

Consciousness of self weight is important for weight loss

Do we have a real perpception of our weight? Do we know if we are really overweight or not? This is what researchers at the University of Illinois investigated when they surveyed over 3,500 college applicants, as part of the Up Amigos project, a collaboration with the Mexican Universidad Autónoma de San Luis Potosi. More than a third couldn't report their weight accurately, and overweight and obese men were more likely to underestimate their weight than women. 

In contrast to what one would thought, almost half of the male volunteers underestimated their weight. Females were more realistic, as 21.2% believed that they were overweight when 27.8% of women were actually overweight or obese. This is even more worrying in the adolescence. According to figures released by the Centers for Disease Control and the International Journal of Pediatric Obesity, American teens are even less likely to report their weights correctly.

Very few participants in the Mexican study overestimated their weight, but those who did were most often female, younger, had parents with less education, and watched more television. Ideal body image changes with exposure to Western media, the researchers noted. The curvier female figure once appreciated in Latino culture is being replaced by the ultra-thin ideal promoted by Western advertisers.

Genes that can increase the risk of childhood obesity

The Center for Applied Genomics at The Children's Hospital of Philadelphia declare tha they have identified and characterized a genetic predisposition to common childhood obesity. The meta-analysis, by an international collaborative group, the Early Growth Genetics (EGG) Consortium, was published in Nature Genetics, and included 14 previous studies encompassing 5,530 cases of childhood obesity and 8,300 control subjects, all of European ancestry.

Previous studies had identified gene variants contributing to obesity in adults and in children with extreme obesity, but relatively little is known about genes implicated in regular childhood obesity. The study team identified two novel loci, one near the OLFM4 gene on chromosome 13, the other within the HOXB5 gene on chromosome 17. Both loci presented associactions with adult and extreme childhood obesity. However, none of the genes were previously implicated in obesity and although it is known they have functions in the intestine, their precise functional role in obesity is currently unknown.

Source: http://www.ncbi.nlm.nih.gov/pubmed/22484627

Obesity in mice can be ameliorated by transplantation of hypothalamic neurons

The db/db mouse is widely employed as model of morbid obesity and its main feature is that it lacks of the receptor of a hormone called leptin. This hormone plays a major role in the hypothalamus, were things like sleep, thirst, body temperature, and hunger are regulated.

In a recent study published in Science, Czupryn et al., showed that increasing leptin-receptor containing neurons in the hypothalamus could work to help db/db mice to reduce weight. They took newborn db/db mice and controls, and gave them an implant of neurons containing the leptin receptor. After the mice grew up, the authors found that the neurons were able to express the leptin receptor in the hypothalamus. The result was a lower body weight in mice treated with the leptin expressing neurons compared to non-treated db/db mice, but not as low as control mice.

Still, though it’s not the whole answer, it’s an interesting start to understanding not only the role of the hypothalamus in obesity and type 2 diabetes, but also how we might be able to change receptors in the brain to restore leptin sensitivity, and decrease sever obesity and the type 2 diabetes that often goes with it.

Source: Scientific American and
Czupryn, A., Zhou, Y., Chen, X., McNay, D., Anderson, M., Flier, J., & Macklis, J. (2011). Transplanted Hypothalamic Neurons Restore Leptin Signaling and Ameliorate Obesity in db/db Mice Science, 334 (6059), 1133-1137