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Amid an obesity epidemic, the approval of two new obesity drugs might revamp the clinical landscape of obesity treatment.

In June, the FDA approved lorcaserin (Belviq), a prescription weight-loss drug developed by Arena Pharmaceuticals that induces satiety through the activation of the 5HT2C receptor, a subtype of serotonin receptors found only in the brain. In 2010, the FDA had rejected lorcaserin because of evidence that it increased cancer incidence in rats and because its modest efficacy did not outweigh safety concerns. New data presented by the company changed the views of the FDA advisory panel, which concluded that the cancer findings did not apply to humans

The FDA's approval in July of Qsymia, developed by the small drug company Vivus, may signal a greater willingness of the FDA to tolerate certain side effects in an antiobesity drug. Qsymia is a combination of two older drugs, phentermine and topiramate, that reduces hunger by targeting different neurotransmitter systems, mainly norepinephrine but also dopamine and serotonin. Whereas this drug seems to induce more weight loss than lorcaserin in a similar target population (an average of 8.9% at the highest dose compared to placebo), it may cause more serious side effects, including an increased heart rate and increased risk of birth defects.

Antibiotics linked to fat buildup

Antibiotics may plump up cows, pigs, chickens, mice and humans alike, new research suggests.
For decades, low doses of antibiotics have been given to livestock to make the animals grow and bulk up faster, but no one really knew how the drugs promoted growth. Now, researchers led by microbiologist Martin Blaser at the New York University School of Medicine report online August 22 in Nature that antibiotics alter the mix of bacteria in the intestines of mice and cause the rodents to build up more fat than normal.
In a separate study, published online August 21 in the International Journal of Obesity, Blaser’s group found a link between antibiotic use in babies younger than 6 months old and being overweight at age 3. Together, the studies suggest that medications that alter the mix of friendly bacteria in the gut may have lasting effects on body weight.

Although antibiotics are meant to kill bacteria, the researchers found that the total number of bacteria in the mice’s guts didn’t change. But the mix of the microbes did. Mice on antibiotics had more of a type of bacteria called Firmicutes and fewer Bacteroidetes bacteria than did mice in the no-antibiotics group. That shift in the composition of gut bacteria is similar to the mix of microbes previously found in obese people, says study coauthor Ilseung Cho, a gastroenterologist at NYU.

Gut microbes in antibiotic-ingesting mice produced more short-chain fatty acids, a type of fat that cells use for energy. “Essentially you’re getting more fuel from the same amount of starting material,” Cho says.