This is true for two reasons. Not only are many fad diets low fat, but they are also low calorie. Your body is not stupid! It can see that you are not taking in enough energy to support your basal metabolic rate. Your basal metabolic rate is the number of calories that your body requires to run your heart, brain, liver, digestive system, lungs etc. This critical number is very responsive to the environment because back in the good old days food wasn’t widely available. If you weren’t able to find food for a few days then your whole system slowed down to require less calories and protect you from dying.
“When you eat sugary foods, your blood sugar levels rise and your pancreas releases insulin to move the sugar from your blood into your cells to be used or stored,” explains Chere Bork, RDN, a nutritionist and life coach in the Minneapolis–St. Paul area. But if your body is continuously exposed to high levels of insulin, Bork says, “the receptor cells become inefficient and resistant to the effects of insulin,” and this leaves blood glucose levels elevated. It is insulin resistance that promotes the high cholesterol, high glucose, and high blood pressure of metabolic syndrome — also known as insulin resistance syndrome.
Though the above guidelines are important, they are not the only hypertension guidelines and currently there is no consensus on them. In 2014, experts appointed to the Eighth Joint National Committee (JNC 8) proposed a different set of guidelines and blood pressure goals and some physician groups continue to endorse these recommendations. The table below summarizes the new goals or target blood pressure readings for specific populations:
Emerging data suggest an important correlation between metabolic syndrome and risk of stroke.  Each of the components of metabolic syndrome has been associated with elevated stroke risk, and evidence demonstrates a relationship between the collective metabolic syndrome and risk of ischemic stroke.  Metabolic syndrome may also be linked to neuropathy beyond hyperglycemic mechanisms through inflammatory mediators.