For the hardest core amongst you, either seriously determined to improve your body composition or see how far you can take athletic performance, there are a variety of options out there that have shown success for many individuals.  My recommendation is to try any one of these for a month at a time, and seek professional medical advice while doing a lot of self-monitoring if you want to go longer or make a lifetime out of it:

• Ketogenesis, the process by which the body burns fat (technically fatty acids and some amino acids) to produce energy (initially in the form of ketone bodies) is very well known and studied by now.  It is essentially the body’s protective mechanism to survive in the absence of food and glycolysis.  Nutritionally it is a difficult state to maintain, as I believe we evolved our ketogenic abilities to serve us in times of long fasting or famine.  There is a ton of literature on ketosis now, so I will just point you to a few resources, along with a few pointers below:
  • This is one of the more difficult nutritional approaches from a compliance perspective, as the body will default to glycolysis as soon as carbohydrates, alcohol, or excess protein is available.  I found my limit, in the absence of any excessive exercise or other environmental factors, to be ~30 grams of non-fibrous carbs, 1 glass of hard, clear alcohol, and ~180 grams of ‘untargeted’ (not specifically chosen for ketogenic amino acids) proteins.  Ideally no alcohol and only residual carbs from nuts and non-starchy vegetables.
  • That said, if you are interested in biohacking and self-monitoring, the feeling some people get (myself and others I’ve heard from) is incredible.  Mental acuity, reduction in inflammation/pain, constant energy levels, training endurance, etc.  It is a self-experiment worth doing just to see what the body is capable of.
  • Micronutrients and electrolyte levels can be tricky to dial in on a ketogenic diet, and supplementation is generally required (see some resources below for recommendations).  For this reason and the lack of much long-term health data I wouldn’t recommend staying ketogenic for long periods of time without some ‘refeeding’ periods of eating a more whole-food balance.
  • Exogenous ketones are an option for a boost, particularly if you don’t tolerate the additional fat from adding fats like MCT oil to everything.
  • There are now genetic markers correlating to the ketogenic diet response.  In general I’d say that using genetic information to help guide your choices is the wave of the future of personalized nutrition.
  • Dominic D’Agostino is one of the biggest experts in this field, and his website has some fantastic resources: Ketonutrition
  • Here are a couple of approaches that could help you ease into ketosis and perhaps maintain compliance: “Keto reset”; “Keto fasting”
  • Here is another nice resource: Chris Kresser’s keto guide
  • And a macronutrient calorie calculator: Ketogains calculator
• True intermittent fasting.  Many times TRE is called intermittent fasting, which it technically is since there’s a fasting window, but an eating fast was traditionally defined as one that lasted more than a day.  Fasting for longer periods, either regularly (e.g. 1-2 days/week) or more intermittently (e.g. doing a 48 hour fast each month) can extend some of the benefits of TRE.  In particular, autophagy, which kicks in after 14 hours of fasting, will really take place during these longer fasts.  If you have the metabolic flexibility to get into ketosis quickly, that could make these fasts easier.
• Vegetarian, Pescatarian, or Vegan diets can all be very effective.  Whether your primary reason is for health, ethical, or other reasons, these are platforms with templates that can be very healthy.  Not necessarily, though, so watch your carb sources (choose non-starchy veggies and fruit over refined grains), ensure your protein intake is high enough, and watch your fat sources. Here is one good source of information: Naomi Whittel
• If you enjoy structure, then explore other programs, such as Whole 30 or Paleo.  Again, the most important thing to remember is that all of us respond differently to different inputs, so figure out what works best for you and your environment!