weight loss
Taking a New Look at Artificial Sweeteners
Posted on by Dr. Francis Collins
Diet sodas and other treats sweetened with artificial sweeteners are often viewed as guilt-free pleasures. Because such foods are usually lower in calories than those containing natural sugars, many have considered them a good option for people who are trying to lose weight or keep their blood glucose levels in check. But some surprising new research suggests that artificial sweeteners might actually do the opposite, by changing the microbes living in our intestines [1].
To explore the impact of various kinds of sweeteners on the zillions of microbes living in the human intestine (referred to as the gut microbiome), an Israeli research team first turned to mice. One group of mice was given water that contained one of two natural sugars: glucose or sucrose; the other group received water that contained one of three artificial sweeteners: saccharin (the main ingredient in Sweet’N Low®), sucralose (Splenda®), or aspartame (Equal®, Nutrasweet®). Both groups ate a diet of normal mouse chow.
Cancer Cachexia: Might This Molecule Hold the Key?
Posted on by Dr. Francis Collins
Caption: Structure of parathyroid hormone-related protein (PTHrP), which has been implicated in cancer-related cachexia.
Source: The Protein Data Bank
No matter how much high-calorie food they eat or nutritionally fortified shakes they drink, many people with cancer just can’t seem to maintain their body weight. They lose muscle and fat, sometimes becoming so weak that they can’t tolerate further treatment. Called cachexia, this progressive wasting syndrome has long troubled patients and their families, as well as baffled scientists searching for ways to treat or perhaps even prevent it.
Some previous studies [1-3] have observed that humans and mice suffering from cachexia have “activated” brown fat. This type of fat, as I explained in a previous post, has the ability to convert its chemical energy into heat to keep the body warm. Intrigued by these hints, a team led by Bruce Spiegelman of the Dana-Farber Cancer Institute and Harvard Medical School in Boston recently decided to explore whether tumor cells might secrete molecules that spur similar brown fat-like activity, causing a gradual depletion of the body’s energy stores.
Fighting Obesity: New Hopes From Brown Fat
Posted on by Dr. Francis Collins
Caption: Brown fat—actually marked in green on this image—is wrapped around the neck and shoulders. This “shawl” of brown fat warms blood before it travels to the brain.
Illustration: John MacNeill, based on patient imaging software designed by Ilan Tal. Copyright 2011 Joslin Diabetes Center
If you want to lose weight, then you actually want more fat, not less. But you need the right kind: brown fat. This special type of fatty tissue burns calories, puts out heat like a furnace, and helps to keep you trim. White fat, on the other hand, stores extra calories and makes you, well, fat. Wouldn’t it be nice if we could instruct our bodies to make more brown fat, and less white fat? Well, NIH-funded researchers have just taken another step in that direction [1].
New Take On How Gastric Bypass Cures Diabetes
Posted on by Dr. Francis Collins
Caption: This is a PET/CT scan of a rat before (left) and after (right) gastric bypass surgery. This kind of a PET scan shows that after surgery the intestine (the looping structures) are using more glucose, which appear yellow and orange. By comparison the before surgery snapshot (left) reveals that there is very little glucose uptake in the intestines, which are barely visible.
Credit: Courtesy of the Stylopoulos Laboratory
A dramatic, lasting, weight loss treatment for morbidly obese patients is gastric bypass surgery. Although there are many variations of this surgery, each with its signature metabolic pros and cons, the Roux-en-Y bypass is the most popular. The operation involves reducing the stomach size by 90% (which restricts food intake) and reconnecting the remaining stomach pouch to a latter section of the small intestine called the jejunum. Food thus “bypasses” digestion in the stomach and the upper portion of the small intestine. The result of this gastrointestinal re-engineering is that less food is eaten and fewer calories are absorbed in the gut.
Weighing in on Sugary Drinks
Posted on by Dr. Francis Collins
Drinking the occasional sugar-sweetened beverage, be it soda, an energy drink, sweetened water, or fruit punch, isn’t going to make you fat. But it’s now clear that many children and adults are at risk for gaining weight if they consume too much of these products.
I want to share new research from three recent papers in the New England Journal of Medicine (NEJM) because, together, they provide some of the most compelling evidence of the role of sugary drinks in childhood obesity, which affects nearly one-fifth of young people between the ages of 6 and 19.
In the first study [1], researchers randomly assigned 641 normal-weight school children between the ages of 4 and 12 to one of two groups. The first group received an 8 oz sugary drink each day; the second received the artificially sweetened version. After 18 months, it was clear that the kids consuming the sugary drink had gained about 2.25 pounds more weight, compared with the kids drinking the zero calorie drinks. They also packed on more fat.
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