For women who’ve tried keto, or any of the low-carb diets, this story probably sounds familiar: “You see someone who’s lost a lot of weight by changing to a high-fat diet, so you decide to try it,” narrates Cate Shanahan, MD, a Cornell-educated physician and consulting nutritionist for the Los Angeles Lakers. “But after a week or two, you feel horrible — and worse, you’ re not losing weight. In that moment, it’s easy to assume, “Well, I guess a low-carb diet just isn’t for me.” But that’s not necessarily the case.”
There’s plenty of proof that low-carb dieting can work wonders for women: In a Danish study, postmenopausal women on a high-fat, Atkins-style diet lost five times more weight than those on a low-fat diet. And low-carb plans have also been shown to improve memory by 62 percent, boost mood by 52 percent, enhance sleep quality by 21 percent and decrease levels of heart-harming triglycerides by 300 percent.
So why does this way of eating fail to deliver for so many of us? As scientists at the Yale School of Medicine explain, if we maintain a high-carb diet over time-which most of us do since the standard American diet is so high in carbs-our mitochondria (the body’s energy production engines) shift from burning fatty acids to burning carbs and sugar.
While this is necessary to help the body metabolize the carbs and sugar we eat, there’s a long-term downside: The process of burning sugar causes the mitochondria to produce damaging cellular debris and free radicals, says nutrition expert Mark Sisson. This shortens the life span of the mitochondria and makes it harder for them to burn fatty acids when we do consume a high-fat meal.
As we age, it becomes increasingly difficult to shift the mitochondria back into fat-burning mode. “The negative effects of a carb-and-sugar-burning system build up over time,” says Sisson. “By the time most of us are 40, the body no longer has the machinery it needs to burn fat for energy.” And that means that when you switch to a low-carb diet like Keto and eliminate the carbs that your mitochondria have grown accustomed to burning, your body won’t be able to create enough energy to fuel all of its essential functions — and you end up feeling tired, foggy, achy, and ravenous.
The good news: It is possible to turn an over-40 metabolism into a fat-burning machine. “The key is to prompt the body to activate the genes that strengthen the mitochondria,” says Sisson. The best way to do that, he adds, is to fill up on healthy fats (which switch on the genes that fire up fat burning) without drastically cutting your carb intake (to ensure the mitochondria that are set to carb-burning get the fuel they need). Science suggests that within 21 days, your body will have created new, healthy mitochondria that have never been damaged by burning sugar and are fully primed to burn fat so you can get all the benefits of an keto-style diet.
“The most dramatic benefit is the quick and efficient reduction of excess body fat,” says Sisson, “but you’ also notice a regulation of your appetite such that you feel alert, well-nourished and rarely hungry.” And science backs him up: Researchers at Texas Tech University in Lubbock found that healthy fats decrease the production of hormones that send hunger signals to the brain.
Weight loss is just the beginning. Women FIRST spoke to report steadier moods, fewer body aches, and lower cholesterol. “It’ like discovering a hidden superpower that stabilizes your energy, mood and brain function,” says Sisson. Read on to discover the strategies that will transform your health.
How Healthy Fat Speeds Weight Loss
Filling up on healthy fat and slowly cutting out carbs revitalizes the body’s ability to burn stored fat. The payoff: effortless weight loss, plus reductions in cholesterol and heart disease risk. And three weeks is all it takes, asserts diet expert Mark Sisson, “Just 21 days will give the body time to rebuild its metabolic machinery so it can efficiently burn fat for fuel.”
At each meal, you’ ll load up on healthy plant-based fats, like avocado, olives, coconut (including coconut oil, coconut milk, and coconut butter), nuts and seeds (including unsweetened nut and seed butters and nut milks) as well as full-fat dairy products from pastured cows (like butter, heavy cream and cheese). These healthy fats help the body switch over to a fat-burning metabolism by activating the genes that create healthy new mitochondria. Sisson explains, “Your main goal is to increase your healthy fat intake so you feel satisfied and don’ struggle as the body changes its fuel source.”
Fill the rest of your plate with unlimited non-starchy vegetables like leafy greens, mushrooms, asparagus and peppers; and 4 oz. of lean protein like chicken breast, ground turkey, flank steak and salmon. Thankfully, there is no need to worry about counting calories or carbohydrate grams. Instead, Sisson recommends eating a small serving of complex carbs, like half of a sweet potato or 1/4 cup of quinoa or brown rice, at least once each day to provide the body with the fuel it needs while it switches over into a fat-burning state.
To ensure the pounds melt away during this 21-day metabolism makeover, eliminate processed carbs- including refined grains and sugars. You’ also eliminate processed fats, including polyunsaturated fats (like canola, soy, cottonseed, corn and vegetable oils). “The type of fat you’ re eating impacts how you feel during the transition,” says integrative physician Cate Shanahan, M.D., author of Deep Nutrition (Flatiron, 2017). As she explains, polyunsaturated fats can slow weight loss and irritate the digestive tract, making a keto-style diet uncomfortable and ineffective.
To further speed weight loss, try these success strategies:
Fat-load at breakfast.
“I advise my patients to eat a carb-free breakfast,” says Dr. Shanahan. Why? After fasting for at least eight hours overnight, hormones are primed to quickly and efficiently mobilize energy in the morning. “We can leverage the hormones to teach the body, This is what I want you to use for energy.”
For a simple way to up your intake of the healthy fats that will reprogram your mitochondria to boost fat burn for the entire day, enjoy breakfast made with coconut oil (like a two-egg omelet fried in 1 Tbs. of coconut oil with two slices of bacon).
Eat when you’re hungry.
Between-meal hunger is often a sign that your body is craving the high-quality fats it needs to rebuild its metabolic machinery, says Sisson. That’ when he recommends reaching for a high-fat snack (see examples at right). But if you don’t feel hungry, there’s no reason to eat just because it’ a designated mealtime. “When you become efficient at accessing and burning stored fat for energy, you’ have all the energy you need,” he says. “You won’ feel compelled to eat.”
Sprinkle on the salt.
A healthy high-fat diet is rich in vitamins and minerals-but new research in the European Journal of Clinical Nutrition found that the food formula caused women’ iodine levels to plummet by 56 percent over six months. That’ a problem since iodine is essential to the production of metabolism-revving hormones. To avoid shortfalls, enjoy two to three daily servings of iodinerich foods (like 1/4 tsp. of iodized salt, 2 eggs, 3 oz. of cod or 6 oz. of tuna).
Burn fat with zzzs.
“Cortisol strongly promotes sugar cravings and fat storage,” says Sisson-but studies show regularly getting quality sleep cuts levels of the stress hormone by 45 percent. If you struggle to get 8 hours a night, try to ensure that you’ re sleeping in a cool environment. Researchers at the National Institutes of Health report that keeping your bedroom at 66°F can help you drift off 40 percent faster and sleep more soundly all night.
This story originally appeared in our print magazine.