I got a lot of questions about the ketogenic diet in class today. It seems to be all the craze in fitness now, and it is reasonable to question whether it would work? In short, you will lose weight on the ketogenic diet (provided you are hypocaloric, of course), but there are some caveats.
How does the ketogenic diet work? Basically, it forces the body to burn fat inefficiently—energy stored in fat is lost at a faster rate. A ketogenic diet involves very low carbohydrates (usually less than 30 grams) and high fat. Fats need some carbohydrate to be adequately metabolized (in the Krebs cycle or tricarboxylic acid cycle). In the absence of carbohydrates, oxaloacetate—the final substrate in the TCA cycle—is converted to pyruvate and acetyl CoA gets converted into ketones. This leaves a lot of energy wasted and one burns through fat.
Ketosis is fine for the overweight non-exerciser, but I would not recommend the diet for an athlete or someone who is training really hard. Some claim that you become “fat adapted”—meaning that the body learns to prefer fats over carbohydrates for energy. To some extent this is true, but I question to what extent, and the evidence is not substantial. If you are lifting weights and doing little to no cardio, you may not notice any great difference. If you are lifting hard and doing some additional conditioning, you will likely feel sluggish. And if one can become “fat-adapted” they have to be all-in—that means giving up carbs altogether (no more pasta, pizza, beer, etc.). You can eat a lot of meat and enjoy (healthy) fats, though.
In my opinion, the ketogenic diet is best for those who are significantly overweight and those who are lean and looking to cut the final bit of fat for show. Those of us in the middle can stand to cut the carbs some (especially carbs with a high glycemic index), but are best to cut our calories to a reasonable level and just be smart with our macro balance.
Diet is a lifestyle. The ketogenic diet is not something one does for a few weeks to get ready for the beach. To be most effective it needs to be a long-term strategy. Some can manage. Others cannot. I cannot. I can limit carbs, but below 0.5 g per pound of bodyweight (about 115 g for me) is too low. I certainly can’t do less than 30 g.
If you want to maintain a more active lifestyle and enjoy some carbs, I would suggest trying to limit carbs to between 0.5 and 1.0 g per lb. If you feel sluggish in your workouts, add more carbs (and cut calories from fat). Optimal protein is easily set at 1 g per lb.
There is nothing inherently unhealthy about the ketogenic diet. It has long been recommended for epileptics and other medical conditions. There may be some concerns about certain nutrient lacking from cutting foods from the basic diet, but selecting low carb and nutrient dense fruits and vegetables can help.
Overall, if the goal is to lose fat, choose a healthy plan that you can stick to for life and start by being hypocaloric. Restrict carbs—or not—based on your activity level. Being able to perform physical exercise at the highest possible level will allow (require) you to eat more while still cutting fat. In the end, you must do what works for you.
Be your best today; be better tomorrow.
Carpe momento!