NEW YORK• Search for "hormone diet" and there are more than 30 recent books on the topic. The authors say the reason people older than 35 struggle to lose weight does not have to do with eating too much or not exercising enough.
They note it is your hormones working against you.
According to these books, you can "trick your metabolism". They claim that all you need to do is eat the right foods and take the right supplements, and you will unlock the secret to lasting weight loss.
But is there any evidence these diets work? The 20/30 Fast Track Hormone Weight Loss Plan is sold at weight-loss centres across the United States and Canada and led by "wellness experts" who take the company's private training, but have no other credentials.
This programme claims to promote rapid weight loss by affecting seven different hormones that make it "impossible for you to lose weight" such as insulin, which moves sugar from your blood into your cells; cortisol, the "stress hormone"; sex hormones such as testosterone and estrogen; and thyroid hormones.
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.
So do "hormone diets" lead to quick and easy weight loss?
"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 professor of medicine Franck Mauvais-Jarvis at Tulane University's medical school.
Mr Suneil Koliwad is an associate professor of endocrinology in the University of California at San Francisco Diabetes Centre. "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. Those studies haven't been done yet."
Though people do not know enough about all the interactions between diet, hormones and weight loss to adjust them to promote rapid weight loss, what is known is that certain ways of eating help keep hormones in balance, which may support weight-loss efforts.
Here is what you can do to promote hormonal balance. Maintain a healthy weight: Being at a healthy weight is key to balancing levels of several hormones, but a complicated diet is not the answer. 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: Overall, whole foods that are rich in fibre, vitamins and minerals, and phytochemicals promote healthy hormone levels.
Hormones such as insulin, cortisol and sex hormones can be negatively affected by a lower-quality diet, such as one that has lots of refined carbohydrates along with hydrogenated and saturated fats from fried foods, fatty meats and highly processed foods. Follow a Mediterranean eating pattern: Eating plenty of colourful vegetables and fruit along with heart-healthy fats such as olive oil and nuts as well as fish and vegetarian proteins appears to be one of the healthiest ways to promote weight loss and prevent chronic diseases. Have protein-rich foods at each meal: Eating foods that are a good source of protein lowers levels of ghrelin, a hormone that makes you feel hungry, and raises levels of hormones that help you feel full.
The bottom line is that hormone diets are a repackaging of other weight-loss diets that do not have enough evidence to support claims.
"When it comes to weight loss, there isn't just one piece of the puzzle to focus on," Mr Koliwad said. "Just because we can measure hormone levels doesn't mean we can adjust them in a desired direction."