Whenever my energy level is inexplicably low as it was on a hike last week, I consume more of the good fats. We get our energy either from carbohydrates or fat.

And now that I eat very few carbs to control my blood glucose level and my weight, I need to get most of my energy from the fat in my diet. But sometimes in my quest to control my weight I don't get enough of either.

Big mistake.

But what are the good fats? They are those with the highest proportion of monounsaturated fatty acids, explains Dr. Dick Williams. He is a consultant to BalancePoint Health, a cholesterol, weight loss, and diabetes control program headquartered in Boulder, Colorado.

"When you stop burning carbohydrates for energy, you need to turn on your fat burner," Dr. Williams told us at the most recent meeting of our local diabetes support group. "Some of the best examples of monounsaturated fats are avocados, olive oil, and nuts -- especially almonds, pecans, and walnuts."

Monounsaturated fats are the best fats because several studies have show that when we replace foods high in saturated fatty acids with monounsaturated-rich foods, we can reduce our LDL cholesterol level. This is in fact one key to the BalancePoint Health program.

"Burning monounsaturated fats," Dr. Williams says, "provides about three times as much caloric energy than carbs, gram for gram, and does not store glucose in the liver or triglycerides around the middle (part of metabolic syndrome ) as do other kinds of fats. Those other fats have a very high risk for a cardiac event -- or death."

I love the taste of macadamia nuts, as I told Dr. Williams. He, however, prefers almonds, pecans, and walnuts, because they are lower in saturated fats. Of these nuts almonds are lowest with 4 grams of saturated fats per 100 grams. Walnuts and pecans have 6 grams, and macadamia nuts have 12, according to the USDA National Nutrient Database.

But, like most things in life, we have to balance the trade offs. Pecans have only 4 grams of net carbs (subtracting fiber from total carbs), macadamia nuts have 5, walnuts have 7 and almonds have 9.

In terms of monounsaturated fat content macadamia nuts are best, 59 grams. Pecans have 41, almonds have 31, and walnuts only 9.

Yet another consideration is the omega 6/omega 3 ratio, according to Dr. Loren Cordain's Paleo Diet. Walnuts have the best ratio, 4.2, followed by macadamia nuts, 6.3 and pecans 20.9. Almonds have no measurable omega 3, so its ratio is infinitely high.

We can obviously choose more than one way to weigh these four factors. But by assigning ranking points to each nut and totalling the points, almonds and walnuts rank equally high followed by pecans and then by macadamia nuts. Back to almonds for me!

Polyunsaturated are as a type the second best. They include a great class of fats known as omega 3 fatty acids that are essential to our health. The main sources of omega 3 fats come from cold-water fish like salmon and sardines. But other foods high in polyunsaturated fats aren't good for us, and they include most vegetable oils. They aren't good for us because they come largely from omega 6 fats that we already get too much of in our diet compared with the amount of omega 3 fats that we eat.