Research

        Fish story: A study of Tanzanian tribes shows that a tribe following a diet rich in fish had lower levels of the hormone leptin than a tribe following a primarily vegetarian diet.

        Leptin, a satiety factor, is secreted by fat tissue. In normal-weight people, the hormone tells people when they've eaten enough. High leptin levels have been associated with obesity and increased risk for cardiovascular disease.

        As people gain weight, the body may stop listening to the leptin message, leading to increased production of the hormone, says Dr. Virend K. Somers, a cardiologist at the Mayo Clinic in Rochester, Minn.

        But researchers found that the fish-eating tribe had lower leptin levels than their vegetarian neighbors, even though they also had higher BMIs (body mass indexes), which measure body fat based on height and weight.

        “We speculate that a fish diet may change the relationship between leptin and body fat and somehow make the body more sensitive to the leptin message.”

        The study was published this month in Circulation: Journal of the American Heart Association.

Just in

        Phase: Exercising later in the menstrual cycle could help women burn more fat and feel less fatigued, say researchers in Australia.

        That's one of the early findings in a study on the little-known impact of the menstrual cycle on women's exercise.

        “Results suggest that exercise performance is improved during the later part of the menstrual cycle, when circulating concentrations of ovarian hormones (estrogen and progesterone) are high,” says researcher Leanne Redman of the University of Adelaide.

        The hormones promote the use of fats as an energy source to support exercise. Fats provide a more efficient delivery of energy and lower levels of waste products, which translates into lower fatigue.

        Ms. Redman says the effects of the menstrual cycle should be considered as women plan their exercise and weight-management routines.

Sitings

        Click here: Check out www.bikehighway.com for cycling routes, a chat board, product reviews and tips for improving your cycling performance.

Nutrition

        Not sweet: Sugar-free cookies and other snacks aren't necessarily great nutrition bargains for diabetics or people watching their weight, says Karen Collins, a registered dietitian with the American Institute of Cancer Research.

        Ms. Collins advises consumers to check the calorie count on the nutrition label: The total might not be lower for the sugar-free version than for the regular version. And new nutrition advice for diabetics emphasizes looking at total carbohydrate consumption — not just how much sugar they're eating.

Shelf help

        New plan: Is Your Thyroid Making You Fat? (Warner Books; $13.95) by Dr. Sanford Siegal suggests that a sluggish thyroid might be the culprit for those of us who never lose weight even though we're always dieting and exercising.

        Contact Peggy O'Farrell by phone: 768-8510; fax: 768-8330; e-mail: pofarrell@enquirer.com.

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