The word “Keto” has practically lost all meaning because it is excessively overused for marketing purposes in the current mileau. So, let’s define “Keto” to be a diet rich in fats (75% of calories), moderate in proteins (20% of calories) and low in carbohydrate (5% of calories). I prefer the name, High Healthy Fat (HHF) diet.
Ancestral diets consisted mainly of meats and low carbohydrate food sources like grasses, with an absence of added refined carbohydrates in foods and beverages. About 200 years ago, it is estimated, humans ate 3 grams of sugar per day. But by 1970, we consumed 155 grams daily, and today, 190 grams. Carbohydrates are also not an obligate, “essential” macro nutrient in our diets, because we can synthesize (via a process known as gluconeogenesis) all we need. Clearly, we did not evolve as a species on the current sugar-laden diets that promote obesity, and contribute to metabolic syndrome and obesity. Moreover, there is not good reason for consuming excessive simple sugars, excepting needs of certain athletes, and even then, typical “weekend warriors” do not need to consume excessive sugars while exercising.
So, keto diets are absolutely safe for all age categories, possibly even infants. Human breast milk contains lactose as a sweet carbohydrate source, along with specialized sialic acid-containing complex carbohydrates that bind toxins; but also ketogenic compounds like medium chain triglycerides (MCTs), to supply energy in between breast feedings.
In past generations, a Keto diet would be easy to follow because sugars were not added to foods in excessive amounts. The challenge today, is that to stay Keto, one must avoid most snack foods, desserts, processed cereals and grains, and even some meats (sugar added for flavor and browning). Possible to stay keto in the long run, yes, but not without challenges, particularly when eating away from home in markets and restaurants. Variants of the Keto diets, such as cyclical- and mixed Keto diets, where Keto is varied with carbs (low glycemic ones) on some days are much easier to follow and adhere to. I would recommend these variants and also recommend not to become too excessive and over regimented about carb indulgences. I suggest to my patients, they throw away their Urinary Keto sticks. There is fear amongst keto enthusiasts that having carb indulgences will take them out of their fat burning/beneficial ketogenic metabolic mode, but this is an understudied area. Consuming high grade MCT oils, like C8 MCTs oilsm or exogenous ketone body salts, make it easier to return to this ketogenic metabolic state, which resembles a fasted state metabolically.
Since, the largest component of a Keto diet is fat, my biggest concern with Keto is that the fats consumed may not be healthy ones. Examples of undesirable fats include excessive amounts of coconut oil, deep fried fats, lard, and oxidized/rancid fats. A certified nutritionist, particularly one with an expertise in fats, is a great resource. The carbohydrates consumed should be of the low glycemic, less processed variety. Go Keto.