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 Dietary Approaches to Stop Hypertension, or DASH, diet has been consistently ranked by US News & World Report as a top diet for heart health and weight loss, and it’s no surprise why. Unlike fad diets that call for extreme calorie or food-group restrictions without scientific evidence that supports their efficacy, the DASH diet involves making manageable dietary changes that are flexible and rooted in proven nutritional advice.
The overall goal of the DASH Diet — short for Dietary Approaches to Stop Hypertension — is to lower your consumption of sodium, which aids in lowering your blood pressure. Since the diet focuses on eating the right foods with the right portions, it's also effective for short- and long-term weight loss. Find out more about the DASH Diet and if it's right for you.
If the liver is resistant to insulin, that's a bad sign for the rest of the body and could mean there's an increased risk of developing type 2 diabetes, the researchers said. What's more, these results are concerning because overweight patients seeking to reduce their risk of type 2 diabetes by following a ketogenic diet could unintentionally be increasing their risk for developing the disease, at least in the first few days of their diet. 
Sleep enough – for most people at least seven hours per night on average – and keep stress under control. Sleep deprivation and stress hormones raise blood sugar levels, slowing ketosis and weight loss a bit. Plus they might make it harder to stick to a keto diet, and resist temptations. So while handling sleep and stress will not get you into ketosis on it’s own, it’s still worth thinking about.
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