As a registered dietitian, I have found that my clients are increasingly asking about books and programs that claim you can adjust your hormones with diet to lose weight quickly and easily.
Search for "hormone diet" and there are more than 30 recent diet books on the topic. The authors 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 centres across the United States and Canada and is led by "wellness experts" who take the company's private training but have no other credentials.
This program claims to promote rapid weight loss - 20 pounds in 30 days - 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. This program also requires the purchase of "homeopathic drops" that come with no evidence supporting their efficacy or safety.
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," Franck Mauvais-Jarvis, a professor of medicine at Tulane University in Louisiana's medical school, wrote in an email.
Why is the hormone story such a complicated one? Hormones are chemical messengers that coordinate or control processes throughout your body. There are at least 60 different 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 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," he says. "Those studies haven't been done yet."
So diets that claim to help you "hack your hormones" for weight loss don't have the evidence to back it up.
Plus, a healthy rate of weight loss, according to the Centres for Disease Control and Prevention, is one to two pounds (0.5kg-1kg) per week, which would be four to eight pounds (1.8kg-3.6kg) per month. Diets that promise faster weight loss aren't promoting healthy, sustainable changes and often lead to weight regain. Also, yo-yo dieting is hard on your heart - and self-esteem.
(An important note: These "hormone diets" are promoted to the general population wanting to lose weight and are very different from the approach used to manage hormone levels in individuals who have a true hormonal imbalance. If you think your thyroid hormones or other hormones could be off, it's important to see an endocrinologist. Hormone imbalances are medical conditions that often require the use of medications.)
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.
Here's 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 isn't 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, diets that are high in a variety of 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.
To reduce elevated insulin levels, eating better-quality carbohydrate sources and less carbohydrates overall may help.
Higher-quality carbohydrates tend to be lower on the glycemic index, minimally processed and higher in fibre. Examples include whole grains such as 100 percent stone-ground whole wheat, rolled or steel-cut oats and barley, pulses such as lentils and chickpeas, sweet potatoes, and berries.
There is also some evidence that low-carb diets can help lower elevated insulin levels.
Eating too much or not enough is also not desirable from a hormone perspective: Overeating can cause insulin levels to rise, while undereating or chronic dieting negatively affects levels of cortisol and sex hormones.
Follow a Mediterranean eating pattern
Eating plenty of colorful 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. It may also make your cells more sensitive to insulin, reducing the risk of Type 2 diabetes.
In particular, oily fish contains long-chain omega-3 fatty acids which may help reduce insulin resistance, a risk-factor for Type 2 diabetes.
Having healthy fats in your meals and snacks triggers the release of hormones that help you feel more satiated, which can support weight loss.
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.
To feel more satisfied, aim to get between 20 to 30 grams of protein at each meal. This would be about three ounces of chicken, fish or meat (about the size of the palm of your hand), about a cup of lentils or tofu or a cup of Greek yogurt or cottage cheese.
Cardiovascular exercise and resistance training have been shown to positively impact insulin levels and balance testosterone levels, which help you retain muscle mass as you age.
Stress is an inevitable part of life, but managing it is essential to your overall health and well-being. Stress management 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 of sleep a night can help boost low testosterone levels and have a positive impact on cortisol, leptin and insulin levels.
The bottom line is that "hormone diets" are a repackaging of other weight-loss diets that don't have enough evidence to support their claims.
"When it comes to weight loss, there isn't just one piece of the puzzle to focus on," Koliwad says. "Just because we can measure hormone levels doesn't mean we can adjust them in a desired direction."