The keto diet changes the way your body converts food into energy. Eating a lot of fat and very few carbs puts you in ketosis, a metabolic state where your body burns fat instead of carbs for fuel. When your body is unable to get glucose from carbs, your liver converts fatty acids from your diet into ketones, an alternative source of energy. Burning ketones in place of glucose reduces inflammation and spurs weight loss.[1]
Of course, many dieters regain what they lose, and this study cannot establish whether participants will be able to sustain their new habits. While people on average lost a significant amount of weight in the study, there was also wide variability in both groups. Some people gained weight, and some lost as much as 50 to 60 pounds. Dr. Gardner said that the people who lost the most weight reported that the study had “changed their relationship with food.” They no longer ate in their cars or in front of their television screens, and they were cooking more at home and sitting down to eat dinner with their families, for example.
“We really stressed to both groups again and again that we wanted them to eat high-quality foods,” Dr. Gardner said. “We told them all that we wanted them to minimize added sugar and refined grains and eat more vegetables and whole foods. We said, ‘Don’t go out and buy a low-fat brownie just because it says low fat. And those low-carb chips — don’t buy them, because they’re still chips and that’s gaming the system.’”
Take action: Aerobic exercise has always been regarded as critical to improving brain health, but strength training is also key. In fact, the two modes of exercise benefit the brain differently, which is why it’s best to do both. In a 2013 study published in the Journal of Aging Research, the authors found that both cardio exercise and strength training improved spatial memory (for example, remembering where objects were placed in a room) in women ages 70 to 80. Cardio alone improved verbal memory (for example, being able to remember a list of words after a distraction). And in a 2012 study from the Archives of Internal Medicine, women in their 70s who strength-trained improved their associative memory, meaning that they remembered pairs of pictures that they had been shown earlier. This is the kind of memory that allows you to remember two pieces of information at once, like picturing not just your keys but also where you placed them.
“This is a great way of eating that I highly recommend to many clients, and I even model in my own life,” says Elizabeth Shaw, RDN, who is in private practice in San Diego and is the co-author of Fertility Foods Cookbook. “Since the premise of the diet is designed to help people who have high blood pressure, low-sodium foods are recommended. But considering that most Americans exceed their daily sodium levels anyway, it’s not surprising that dietitians recommend this style of eating for treating many different conditions, such as heart disease and obesity.”
Diarrhea can also be due to a lack of fiber in the diet, says Kizer, which can happen when someone cuts way back on carbs (like whole-grain bread and pasta) and doesn’t supplement with other fiber-rich foods, like vegetables. It can also be caused by an intolerance to dairy or artificial sweeteners—things you might be eating more of since switching to a high-fat, low-carb lifestyle.
Those issues can be part of what's known as the “keto flu,” Warren says. Other side effects of the keto diet, all of which are tied to carb withdrawal, can include lightheadedness, nausea, mental fog, cramps, and headaches, in addition to tiredness. Luckily, the keto flu doesn't usually last more than a week—which is coincidentally about when people start to see the number on the scale go down, says Warren.

The end is here! Three cheers for all your hard work. But that doesn't mean it's time to put on the brakes. To maintain your weight, you still have to make those smart choices at restaurants, work, and home. Look into getting a diet confidante, who you can chat with once a week about your eating highs and oh-no's. And stick to using that scale so you can be proactive if a few extra pounds creep back on. Don't let your exercise routine change, either, because even if you don't have any more pounds to lose, you'll still be working out your ticker. And we heart that!
Keto breath, on the other hand, is less of a side-effect and more of a harmless inconvenience (your breath literally smells like nail polish remover). Basically, when your body breaks down all that extra fat on the keto diet, it produces ketones—one of which is the chemical acetone, Keatley previously told WomensHealthMag.com. (Yes, the same stuff that's in nail polish remover.)
In addition, the healthy habits and kinds of foods recommended on the Mayo Clinic Diet — including lots of vegetables, fruits, whole grains, nuts, beans, fish and healthy fats — can further reduce your risk of certain health conditions. The Mayo Clinic Diet is meant to be positive, practical, sustainable and enjoyable, so you can enjoy a happier, healthier life over the long term.
To get the most benefit from the Keto diet, you should stay physically active. You might need to take it easier during the early ketosis period, especially if you feel fatigued or lightheaded. Walking, running, doing aerobics, weightlifting, training with kettlebells or whatever workout you prefer will boost your energy further. You can find books and online resources on how to adapt Keto meals or snacks for athletic training.

It seems strange that a diet that calls for more fat can raise “good” cholesterol and lower “bad” cholesterol, but ketogenic diets are linked to just that. It may be because the lower levels of insulin that result from these diets can stop your body from making more cholesterol. That means you’re less likely to have high blood pressure, hardened arteries, heart failure, and other heart conditions. 
If the diet is a quick fix rather than one that promotes lasting lifestyle changes, this could pose a problem. In particular, extreme diets that promise big weight loss up front aren’t always sustainable — and you may end up overeating or even binge eating if you feel deprived. “Consider if the diet’s habits are ones you can continue throughout your lifetime, not just 21 or 30 days,” says Angie Asche, RD, a sports dietitian in Lincoln, Nebraska.
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