Initial human studies that compared fasting every other day to eating less every day showed that both worked about equally for weight loss, though people struggled with the fasting days. So I had written off IF as no better or worse than simply eating less, only far more uncomfortable. My advice was to just stick with the sensible, plant-based, Mediterranean-style diet.
Probably the most popular option is fasting for 16 hours (including sleep), which is usually easy to do on a keto diet. It requires trading breakfast for a cup of coffee (or some other non-caloric fluid) and having lunch as the first meal of the day. Fasting from 8 pm to 12 noon – for example – equals 16 hours of fasting. Another option is to skip dinner: eat breakfast and lunch within 8 hours — for instance, 8 am to 2 pm — and then don’t eat again until 8 am the next morning.
But beyond that, experts aren't convinced that the keto diet has any other scientifically-proven health benefits. In fact, it may have some distinct downsides. If you follow the keto diet incorrectly, for example (like by eating lots of saturated fats, versus healthy unsaturated fats), you're at risk of raising your cholesterol levels. “The best strategy to keep your heart healthy is to get as much fat as possible from unsaturated sources such as olive, avocado and canola oils, nuts, seeds, avocados, and olives," says Ansel.
But people who started following the keto diet noticed weight loss for a few reasons: When you eat carbs, your body retains fluid in order to store carbs for energy (you know, in case it needs it). But when you’re not having much in the carb department, you lose this water weight, says Warren. Also, it's easy to go overboard on carbohydrates—but if you're loading up on fat, it may help curb cravings since it keeps you satisfied.
Because people with type 2 diabetes are at an increased risk for cardiovascular disease, there’s a specific concern that the saturated fat in the diet may drive up LDL, or “bad,” cholesterol levels, and further increase the odds of heart problems. If you have type 2 diabetes, talk to your doctor before attempting a ketogenic diet. They may recommend a different weight-loss diet for you, like a reduced-calorie diet, to manage diabetes. Those with epilepsy should also consult their doctor before using this as part of their treatment plan.
People claiming huge benefits of these supplements – despite the lack of solid scientific support – may sometimes have a financial reason to believe in the supplements. Some of these products are sold under a multi-level marketing arrangement, where sales people are paid based on commission. For example, the company Prüvit sells drinkable ketones, called KETO//OS with a multi-level marketing structure.
A ketogenic diet helps control blood sugar levels. It is excellent for managing type 2 diabetes, sometimes even leading to complete reversal of the disease. This has been proven in studies. It makes perfect sense since keto lowers blood-sugar levels, reduces the need of medications and reduces the potentially negative impact of high insulin levels.
Gary D. Foster, Ph.D., Holly R. Wyatt, M.D., James O. Hill, Ph.D., Brian G. McGuckin, Ed.M., Carrie Brill, B.S., B. Selma Mohammed, M.D., Ph.D., Philippe O. Szapary, M.D., Daniel J. Rader, M.D., Joel S. Edman, D.Sc., and Samuel Klein, M.D., “A Randomized Trial of a Low-Carbohydrate Diet for Obesity — NEJM,” N Engl J Med 2003; 348:2082- 2090. http://www.nejm.org/doi/full/10.1056/NEJMoa022207.
There are three instances where there’s research to back up a ketogenic diet, including to help control type 2 diabetes, as part of epilepsy treatment, or for weight loss, says Mattinson. “In terms of diabetes, there is some promising research showing that the ketogenic diet may improve glycemic control. It may cause a reduction in A1C — a key test for diabetes that measures a person’s average blood sugar control over two to three months — something that may help you reduce medication use,” she says.
AN IMPORTANT CAVEAT: Intermittent Fasting can be more complex for people who have issues with blood sugar regulation, suffer from hypoglycemia, have diabetes, etc. If you fit into this category, check with your doctor or dietitian before adjusting your eating schedule. It also affects women differently (there’s a whole section dedicated to that here).
For even more impressive effects on body composition, aim for exercise forms which elicit a positive hormonal response. This means lifting really heavy things (strength training), or interval training. Such exercise increases levels of the sex hormone testosterone (primarily in men) as well as growth hormone. Not only do greater levels of these hormones increase your muscle mass, but they also decrease your visceral fat (belly fat) in the long term.