The Longevity Diet

The Longevity Diet is a book about calorie restriction and how to go about trying it. The authors are Brian Delaney, President of the Calorie Restriction Society, and Lisa Walford, the daughter or Dr Roy Walford who was one of the early proponents of calorie restriction for people. They are both well connected to the community that is trying calorie restriction, and well grounded in the science behind it.

From their experience, improvements in health and slower aging come from any regimen that includes reduced calories over what is considered a normal level. So you can eat some high-glycemic food such as rice or potatoes, or eat a really healthy diet where all of your carbohydrates come from vegetables and fruit. You can eat one meal a day, or graze throughout the day. All of the apparent benefits will result as long as you eat enough less than normal.

There are a number of ways to track progress: watch your weight and when it gets to a BMI of 15-16 then eat enough to keep it there; track total calories relative to normal for your body height/frame; or track health markers such as fasting blood sugar, liver function, lipids (e.g. cholesterol, HDL, LDL, triglycerides), blood pressure, and immune system function.

They emphasize repeatedly that you should talk to your doctor or health professional before going on this regimen, and that it is not for everyone. If you are pregnant or want to get pregnant or have certain medical conditions you should definitely NOT use this diet. If you have a lot of weight to lose to get to a low BMI, or if you are over 60, you should definitely take it slow and not make too radical a change.

They make a number of key points:

• Because you are eating a reduced-calorie diet, you have to make sure that you get enough nutrients: protein, fat, calories, essential fatty acids, vitamins, and minerals.
• This is why most practitioners eat all of their carbohydrates in the form of vegetables and fruit, because they have very high nutrition value per calorie. When you eat a lot of calories from starch (bread, potatoes, white rice, other starches) it is very hard to reduce your calorie intake enough and still get enough nutrition.
• If you adopt this regimen, you have to find a way to do it that works for you and lets you enjoy life. Don't stress out about it
• Exercise and managing stress are important for everyone

I really liked their idea of "energy density" and "nutrition density" for food. For example, cheese has high energy density; vegetables have high nutrition density. To feel fuller and to get enough nutrition, you want a lot of your calories to come from high-nutrition, low-energy-density foods. This is a good point for everyone, not just when you are on a calorie restriction diet.

I had a couple of issues with their advice:

• they do not recommend using omega-3 supplements, suggesting that you will get enough omega-3 from a high-nutrient diet. I don't think this is the case, to get enough omega-3 for optimal brain function you almost have to supplement, or eat very expensive grass-fed meat, grass-fed dairy, etc, or eat very large amounts of fish.
• they mention fasting as an alternative for reducing total calories, that this is easier for some people. However, this book was written before research came out that suggests fasting is not healthy on a long-term basis (it looks like one day fasts are fine, so every-other day fasting is an option).
  
• they are convinced that calorie restriction will increase maximum human lifetimes, but I don't think that we know or can say at this point. (It is clear that calorie restriction with good nutrition does increase your life expectancy, but not that you should expect to live past 100 on this regimen.)

There is some research that suggests that the important thing is not the reduced calories, but the hormones that are released when you are hungry. So I think I'm going to try skipping lunch and snacks, having a normal breakfast and dinner, and eating enough at those meals to feel full. I'll continue to track my weight and ongoing blood sugar levels, and see what the effect is

Fascinating stuff, and I recommend the book.