Nutrition Science and Everyday Application - beta v 0.1

202 ALICE CALLAHAN, PHD, HEATHER LEONARD, MED, RDN, AND TAMBERLY POWELL, MS, RDN
Figure 4.18. During starvation or when consuming a low-carbohydrate diet, protein (amino
acids) can be used to make glucose by gluconeogenesis, and fats can be used to make ketones in
the liver. The brain can adapt to using ketones as an energy source in order to conserve protein
and prevent muscle wasting.
Ketone production is important, because ketones can be used by tissues of the body
as a source of energy during starvation or a low carbohydrate diet. Even the brain can
adapt to using ketones as a source of fuel after about three days of starvation or very lowcarbohydrate
diet. This also helps to preserve the protein in the muscle.
Ketones can be excreted in urine, but if ketone production is very high, they begin to
accumulate in the blood, a condition called ketosis. Symptoms of ketosis include sweetsmelling
breath, dry mouth, and reduced appetite. People consuming a very low
carbohydrate diet may be in ketosis, and in fact, this is a goal of the currently popular
ketogenic diet. (Ketones are acidic, so severe ketosis can cause the blood to become too
acidic, a condition called ketoacidosis. This mainly happens with uncontrolled diabetes.)
Is following a ketogenic diet an effective way to lose weight? It can be, but the same
can be said of any diet that severely restricts the types of foods that you’re allowed to
eat. Following a ketogenic diet means eating a high fat diet with very little carbohydrate
and moderate protein. This means eating lots of meat, fish, eggs, cheese, butter, oils, and
low carbohydrate vegetables, and eliminating grain products, beans, and even fruit. With
so many fewer choices, you’re likely to spend more time planning meals and less time
mindlessly snacking. Being in ketosis also seems to reduce appetite, and it causes you to
lose a lot of water weight initially. However, studies show that being in ketosis doesn’t seem
to increase fat-burning or metabolic rate. There are also concerns that the high levels of
saturated fat in most ketogenic diets could increase risk of heart disease in the long term.
Finally, it’s a very difficult diet to maintain for most people, and reverting back to your
previous dietary patterns usually means the weight will come back. The ketogenic diet is also
very similar to the Atkins diet that was all the rage in the 1990’s, and we tend to be skeptical