More than 30 recent diet books allege that the reason people over 35 struggle to lose weight doesn't have to do with eating too much or not exercising enough. They say it's your hormones working against you.
According to these books, you can "trick your metabolism" and "feed your thyroid." They claim that all you need to do is eat the right foods and take the right supplements, and you'll unlock the secret to lasting weight loss.
But is there any evidence these diets work?
The 20/30 Fast Track Hormone Weight Loss Plan isn't a book; it's a pricey program. It's sold at weight-loss centers and is led by "wellness experts" who take the company's private training but have no other credentials.
The diet bans the usual suspects: sugar and sweetened foods and beverages, along with all grains, potatoes and sweet potatoes, beans and lentils, milk, and most fruit.
"I don't know of any diet that will change hormone levels in a way that these hormone changes will be instrumental in promoting weight loss," said Franck Mauvais-Jarvis, a professor of medicine at Tulane University.
Hormones are chemical messengers that coordinate or control processes throughout your body. There are at least 60 hormones in humans, and we're only beginning to understand how what we eat affects them.
Suneil Koliwad is an associate professor of endocrinology in the University of California at San Francisco Diabetes Center.
"It's premature at this point to think anyone knows exactly what components of the diet are needed to manipulate a variety of hormones across the board in specific ways," he says. "Those studies haven't been done yet."
Though we don't know enough about all the interactions between diet, hormones and weight loss to adjust them to promote rapid weight loss, we do know that certain ways of eating help keep our hormones in balance, which may support our weight-loss efforts:
• Maintain a healthy weight: Eating fewer calories, choosing higher-quality and minimally processed foods, and drinking plenty of water are strategies with a lasting impact.
• Focus on diet quality: A variety of whole foods that are rich in fiber, vitamins and minerals, and phytochemicals promote healthy hormone levels. There is also some evidence that low-carb diets can help lower elevated insulin levels.
• Follow a Mediterranean pattern: Eat plenty of colorful vegetables and fruit along with heart-healthy fats such as olive oil and nuts as well as fish and vegetarian proteins. Having healthy fats in your meals and snacks triggers the release of hormones that help you feel more satiated, which can support weight loss.
• Keep moving: Cardiovascular exercise and resistance training have been shown to positively impact insulin levels and balance testosterone levels.
• Manage stress: Techniques such as yoga and meditation can help lower cortisol levels, which can support your weight-loss efforts.
• Get enough sleep: Consistently logging eight hours a night can help boost low testosterone levels and have a positive impact on cortisol, leptin and insulin levels.