Really, it shouldn’t be so difficult to figure out which eating regimen will set fire to fat while maintaining muscle. Fortunately, the International Society of Sports Nutrition just released its position paper, which combs through all existing scientific studies to report how every diet will affect your body composition. Here, we’ve pulled five of the most six-pack-friendly diets and streamlined how they’re great, as well as why they might be right (or wrong) for you—according to the hard science.
A study in the journal Metabolism found that eating half a grapefruit before meals may help reduce visceral fat and lower cholesterol levels. Participants in the 6-week study who ate a Rio Red grapefruit fifteen minutes before each meal saw their waists shrink by up to an inch, and LDL levels drop by 18 points. Though researchers don’t exactly know what makes grapefruit so good at burning fat, they attribute the effects to a combination of phytochemicals and vitamin C found in the tart treat.
While it’s true that low-carb diets do raise the so-called bad LDL-cholesterol in some people, it’s important to note that LDL-C, when influenced by diet, has never been shown to have any effect on cardiovascular risk. Large clinical trials and observational studies show that one’s level of LDL-C and the lowering of LDL-C through diet is not reliably linked to cardiovascular outcomes.21, 22, 23
The Mediterranean Diet was identified in the 1960s as research continued to show populations from Mediterranean regions, particularly Southern Italy, the isle of Crete, and Greece, were considerably healthier, with less incidence of disease and longer lifespans than seen in other regions. Studies indicated that the way these populations ate seemed to be the common denominator and through research, the Mediterranean diet was formally born.
A small Feb. 20, 2017, study looked at the impact of a six-week ketogenic diet on physical fitness and body composition in 42 healthy adults. The study, published in the journal Nutrition & Metabolism, found a mildly negative impact on physical performance in terms of endurance capacity, peak power and faster exhaustion. Overall, researchers concluded, “Our findings lead us to assume that a [ketogenic diet] does not impact physical fitness in a clinically relevant manner that would impair activities of daily living and aerobic training.” The “significant” weight loss of about 4.4 pounds, on average, did not affect muscle mass or function.
This research found the weight loss was slightly greater in the group fasting for two days compared to the other group. It’s worth noting that the participants in these studies were given a huge amount of support, which wouldn’t happen if you were just picking up a book on the 5:2 diet. Overall, there isn’t actually much evidence and we need more data on the long-term success of these diets.’
My husband and I have been doing this diet for a while now. And let me tell you it works. He has lost weight and his blood pressure has gone down!! It isn't a hard diet at all, the first 2 weeks you learn to live without carbs , but that isn't to bad. The 2nd phase you start adding some carbs back along with other foods. It's all about making the right choices.
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.)
DASH was first introduced at a meeting of the American Heart Association in 1996 and later published in the New England Journal of Medicine in 1997.  The DASH trial randomly assigned 456 people to different diets to test the effects of dietary patterns on lowering blood pressure. The authors surmised that eating a diet with many different foods with blood pressure-lowering nutrients would show a greater effect on blood pressure than eating single nutrients, such as found in supplements or in a limited diet. Three diets were tested: 1) a control diet, or a standard American diet, 2) a fruits and vegetables diet, similar to the control diet but providing more fruits and vegetables and less snacks and sweets, and 3) a combination diet rich in fruits, vegetables, nuts, and low-fat dairy foods with reduced amounts of saturated fat, total fat, and cholesterol. The last two diets were richer in nutrients associated with lower blood pressure, such as potassium, magnesium, calcium, fiber, and protein. All three diets provided about 3000 mg sodium, which is more than the recommended amount from the Dietary Guidelines for Americans but less than the average sodium intake for Americans. 
It sounds as if you may have been following a very strict keto protocol. I’m not, and have not followed a ketogenic diet, but am interested in it. I’ve been reading up on it a bit on the blog called Mark’s Daily Apple.* I’ve been following it for several years now, even before Mark tried keto. Based on some of his blog post, both keto related and otherwise, it seems that women do better with slightly more carbs than men. He’s written several blog post specifically for women, including one called 7 Keto Tips for Women, which you may want to read. https://www.marksdailyapple.com/7-keto-tips-for-women/ Then there is this one Where I Part Ways with the Popular Keto Movement https://www.marksdailyapple.com/where-i-part-ways-with-the-popular-keto-movement/ Perhaps the problem wasn’t the keto diet in and of itself, but that you went too low carb for you. It’s worth considering. I’ve also found this site to be pretty interesting https://peterattiamd.com/ Here’s a link to his section on keto https://peterattiamd.com/category/ketosis/ He followed a ketogenic diet for a number of years, though as of 2016 was no longer ketogenic, but definitely eating lower carb than most. (That is under Articles, on the drop down menu, click on Personal.)
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.