A biological basis for obesity
New research has shown that weight gain in obese rats may be due to low activity levels, rather than excessive calorie consumption. The study was carried out as a joint effort by colleagues at the University of Minnesota, the Minnesota Obesity Center and the Mayo Clinic (MN, USA).
The researchers found that lean rats are more sensitive to the activity-stimulating chemical orexin A. Minor physical activities induced by orexin A, such as fidgeting and other movements associated with restlessness, help to control weight by burning calories. “The greater expression of orexin receptors suggests the lean rats’ brains were more sensitive to the orexin the brain produces”, explains Catherine M Kotz, senior researcher for the study. “The results point to a biological basis for being a couch potato.”
Obesity-prone and -resistant rats were developed by selective breeding and then used in a series of experiments in which different amounts of orexin A were given to the rats. Activity levels of individual rats were measured using sensors, revealing that the lean group moved significantly more than the obesity-prone group. Obesity itself was not responsible for reduced activity, as the experiments were carried out while the rats were young, all the same weight and on exactly the same diet.
Previous research has revealed that lean (human) individuals move around 2 h more a day than obese individuals. “Many people focus on diet (to control their weight), but it may be more feasible for some people to stand or move more throughout the day”, comments Dr Kotz.
The full study appears in the American Journal of Physiology–Regulatory, Integrative and Comparative Physiology.
Vegan diet better than medication for diabetes patients?
A multicenter study has demonstrated the benefits of a vegan diet for those with Type 2 diabetes. These are greater than those observed when following the standard American Diabetes Association (ADA) diet and may even be more effective than single-agent therapy with oral diabetes drugs.
Approximately 20 million Americans have Type 2 diabetes and the number of people dying and suffering from diabetes and its complications is expected to approximately triple by 2025. The disease is caused by genetic factors and often brought on by obesity and lack of exercise. There is a high risk to sufferers of complications, such as heart disease, stroke, kidney failure, blindness and limb loss.
In the study, 99 patients were randomly assigned to either a low-fat, low-sugar vegan diet (removing all animal products, including meat, fish and dairy) or the standard ADA diet, which is more tailored and takes into account the patient’s weight and cholesterol. Most patients on the ADA diet cut calories significantly and were advised to eat sugary and starchy foods in moderation. All participants met with advisers weekly for advice on recipes and maintaining their diet, as well as encouragement.
Results showed that while both diets led to improved diabetes management, patients who cut out all meat and dairy lowered their blood sugar levels more than those on the standard ADA diet. After 22 weeks, 43% of participants on the vegan diet compared with 26% of those on the standard diet were able to either cut down or completely stop taking their insulin or glucose-control medication. Beneficial side effects of the diets included weight loss (on average 6.5 kg for vegan dieters vs 3.1 kg for ADA dieters), a decrease in low-density lipoprotein cholesterol levels and improved kidney function. Long-term measures of glucose control, such as a1c, also decreased more for the new vegans (1.23 vs 0.38 points for standard dieters).
Many participants in the study found the vegan diet easier to follow. Over the study period, three people dropped out of the vegan-diet group compared with eight following the ADA-recommended diet. This may be due to the fact that the vegan diet does not involve measuring portions, or calorie or carbohydrate counting. The simplicity and ease of compliance is particularly important when considering the long-term value of such lifestyle changes.
It is hoped that this research will emphasize the role that diet and lifestyle can play in managing diabetes, rather than prescription medication.
Prediabetic state: possibly indicated by carpal tunnel syndrome & Bell’s facial palsy
A cohort study conducted recently in the UK has suggested that carpal tunnel syndrome and Bell’s facial palsy may predate the onset of Type 2 diabetes by up to 10 years.
The study was led by Dr Martin C Gulliford and his team from King’s College London (UK), where medical records from 114 family practices in England and Wales were examined. They discovered from 644,495 patients that 2645 patients were diagnosed with diabetes between November 2003 and October 2004, in comparison with 5294 control subjects who were matched for age, gender and practice.
As published in the August issue of Diabetes Care, medical records (for up to 10 years before diabetes was diagnosed) were evaluated for initial symptoms of carpal tunnel syndrome; subjects diagnosed with Bell’s facial palsy were also identified.
After accounting for other risk factors, the results for the prediabetes group demonstrated that the incidence of carpal tunnel syndrome was 425.1/100,000 person-years versus 260/100,000 in the control group, with relevant risk having a significant statistical value of 1.36 (p = 0.039).
In comparison, Bell’s facial palsy occurred more often in the prediabetic group compared with the control group (81.1 vs 41.2/100,000 person-years). Nevertheless, after adjusting for other risk factors such as age, sex and body mass index (BMI) category, the relative risk statistical value proved insignificant (1.64; p = 0.128).
The incidence of other peripheral nerve disorders were assessed and found to be similar between the two groups. “Hyperglycemia and associated metabolic abnormalities may contribute to causing these important focal peripheral nerve disorders before the diagnosis of diabetes”, Dr Gulliford and his team suggest.
Obesity associated with decreased survival rates in women with ovarian cancer
Results from a new study carried out by researchers at the Cedars–Sinai Medical Center (LA, USA) have confirmed that obesity is associated with a decreased risk of survival in women diagnosed with ovarian cancer. According to the study results, published in Cancer, women who develop ovarian cancer when they are obese have shorter disease-free survival times than those with a lower body mass index (BMI). In addition, the study found that an increase in BMI correlated with a decrease in survival.
The team at Cedars–Sinai used the medical records of 216 women diagnosed with epithelial ovarian cancer to examine the relationship between obestity, ovarian cancer, the biology of tumors and health outcomes. In this group of women, a total of 8% were underweight, 50% were ideal weight, 26% were overweight and 16% were classified as obese. Overall survival was not found to differ significantly between obese compared with ideal-bodyweight patients; however when narrowed down to those patients with advanced disease, an increase in BMI was seen to be associated with a shorter time to cancer occurrence and survival, even after accounting for the obvious increased prevalence of diabetes and hypertension in these patients.
The research team, led by Andrew J Li, are now expected to continue their studies into the molecular mechanisms that underlie this association between obesity and ovarian cancer survival.