How we as individuals respond to foods will determine how restrictive we have to be. That depends largely on how insulin sensitive we are—that is, how well our bodies process the carbohydrates in our diets . And our insulin sensitivity can vary based on how much we’ve been sitting around, how intensely we have exercised, and how much sleep we have gotten, along with other factors.

By “how we as individuals respond to foods,” I mean this:

• How it affects our blood sugar
• Does it trigger cravings and cause us to eat things we shouldn’t (or more than we need to feel full).
• Does it cause our waistlines to expand (or prevent weight loss if that is our goal)
• Does it make our key lab markers worse (HDL, triglycerides,A1C, fasting insulin)
• Does it make us feel worse

Based on those responses, these are the ways we may need to restrict our diets in order to maintain our metabolic health:

• Very insulin sensitive people may be able to maintain their metabolic health by simply cutting back on these processed foods. (By processed foods I mean those containing added sugar, refined carbohydrates such as flour or cornmeal, and those containing unnatural oils and fats.)
• Others may need to eliminate processed foods entirely, but have no need for further restrictions and can eat real foods with substantial starch (e.g., potatoes, oatmeal).
• Some among us will need to go further and eliminate starchy vegetables and grains (e.g., potatoes, oatmeal).
• Others will need to eliminate high-sugar fruits like apples and bananas.
• Some will need to eliminate virtually all carbohydrates from the diet to attain metabolic health (known as a ketogenic diet, or “keto” for short).

It depends. Maintaining metabolic health over the long haul requires that the way we eat be sustainable. For people who think they can’t live without certain foods, that may mean they cheat on occasion (perhaps a weekly sweet treat). For someone else, being sustainable may mean no cheats ever, in the same way someone trying to quit smoking can’t cheat. For some of us, sweets and processed carbs are like cigarettes. We must go cold turkey.

We also need to keep in mind that when we cheat we are shifting our biochemistry in the direction of fat storage, at least for a while. That should motivate us to keep any cheats to a minimum.

If you do decide to have an occasional cheat, here are some guidelines:

• Buy just one serving. Don’t buy a carton of ice cream thinking you’ll have a scoop on occasion. Go to the ice cream shop and buy one scoop in a cup. Don’t buy a box of cookies; buy just one cookie.
• Avoid the thought process, “I’ve blown it for today, so I might as well wait until tomorrow to start eating right again.” The sooner you are back on the wagon the sooner your biochemistry gets back into energy-burning mode, and the sooner your reward center stops clamoring for more.
• Get a small portion. Most of the pleasure comes in the first few bites.
• Make yourself accountable to someone else. If you find yourself at a social event with a lot of bad food around, let someone know you don’t plan to eat it. That helps stiffen will power.
• At social events bring something for yourself that is tasty and satisfying so you won’t be as tempted to eat the other foods on offer.
• Don’t cheat with something that will trigger cravings. I know that if right now I were to eat a single Oreo cookie, someone would likely find me, hours later, passed out in some back alley surrounded by Little Debbie brownie wrappers, a half-eaten Twinkie clutched in my Dorito-stained fingers. So, I don’t eat Oreos.
• Watch out for carb creep, where we gradually increase our carb intake until it starts to affect our metabolic health. Set definite boundaries and have someone hold you accountable.

I see “low carb” this and “keto-friendly” that at the store. Are those okay?

It depends. Some low-carb or “keto friendly” foods are created by companies led by people who really want to provide metabolically healthy options for us. They are minimally processed, using real food as their ingredients. Other companies are just trying to cash in on a growing trend and don’t seem to care much about what they put in their food (I am here thinking of Mission, purveyor of delicious yet nutritionally dubious low-carb tortillas).

A low-carb substitute (for bread, tortillas, cookies, crackers, desserts) may or may not be okay for us, depending on what is in it and how our bodies react to it.

On a low-carb substitute’s package you will typically see a reference to “net carbs.” The idea is that some forms of carbohydrate—fiber and alcohol sugars —are not digested and pass into our gut where some of it is digested by the microbes there, and so don’t affect our blood sugar. That is partially true. The alcohol sugars erythritol and xylitol do not have much effect on our blood sugar, but maltitol and sorbitol do (though not as much as glucose). So read the label carefully. (Some recent research suggests that erythritol can increase blood clotting in unhealthy ways. It may be best to avoid that until the research is in on that.)

Low-carb breads and tortillas typically substitute fiber for starch. Substitute desserts usually substitute alcohol sugars for sucrose.

Some alcohol sugars do provide sweetness without spiking blood sugar, but there isn’t really enough data to know about the health impacts of consuming them (particularly their effect on the microbes in our gut). One observation I have made is that consuming more than a small amount of alcohol sugar sweeteners can have untoward effects. (For a demonstration of the possible effects of overconsuming alcohol sugars, see Daniels, J. (1994); Dumb and Dumber; “Toilet Scene.” [film])

Other non-caloric sweeteners include stevia, which is an extract from a plant; aspartame, created from amino acids; and sucralose, a chemically modified form of a sucrose molecule that we taste the sweetness of but do not metabolize. A newer non-caloric sweetener that is gaining popularity is allulose. It occurs naturally but scientists have learned to synthesize it. There is some evidence that allulose can have positive effects on our microbiome and blood sugar, but it is too early to say for sure.

Eating these substitutes can cause cravings of their own, and if one isn’t careful they can become a larger and larger part of the diet. It is probably best to reserve them for special circumstances rather than using them as staples of your diet.

On the plus side, these substitutes may help some people avoid refined carbs and added sugar, and so can help them to maintain their metabolic health. One might compare it to a cigarette smoker who turns to vaping when unable to quit tobacco. It would be better to do neither, but vaping is (perhaps) less harmful than smoking cigarettes.

In deciding whether to eat one of these substitutes, it is crucial to look past the health claims on the package and pay attention to the nutrition and ingredient labels. To calculate the starch and sugar intake, subtract the fiber and alcohol sugar from the total carbohydrate to get the net carbs. For example, on this package of Mission “Carb Balance” tortillas, we see that it has 12 grams of carbohydrates, 9 grams of which are fiber. Since the fiber is not converted to glucose but passes on into our gut, there are only three grams left to convert to glucose. So far so good.

But then we come to the ingredient label, which is something of a horror show. Interesterified and hydrogenated soybean oils? That sounds like something one might use to refinish a coffee table.

Or how about this SlimFast “Keto Nutty Caramel & Nougat” bar. It has 21 grams of carbohydrate, but after you subtract out the 13 grams of fiber and 5 grams of sugar alcohol, you are left with only 3 grams of net carbs. Seems like a reasonable option.

Until we get to the ingredient label. Egad! Unless you happen to hold a PhD in chemistry, you will likely not know what most of those things are, much less be able to gauge their possible impact on your health.

We should never forget that the food that comes out of the ground or from animals is going to be better for us than that which comes out of a box.

The key distinction is between unprocessed or minimally-processed food and processed food. Unprocessed food would be meat, fish, dairy, eggs, vegetables, and fruit (fresh and frozen), along with herbs and spices. Unprocessed foods don’t have ingredient lists. They come from plants or animals, not things that came out of a lab.

Any packaged foods should be minimally processed (meaning the ingredients are real food). They should be low in sugar (especially added sugar) and low in refined carbohydrate (e.g flour). They should not have industrial vegetable oils (soybean oil, corn oil, etc.).

Most meat should be unprocessed—just meat, though if you are a careful shopper you can find some brands of packaged meats that are minimally processed.

When considering a packaged food, it is important to closely scrutinize the label. For example, here is the label for Kellogg’s Raisin Bran Crunch. The name makes it sound vaguely healthy. Note first of all that it has 68 grams of carbohydrate, of which 28 grams are sugar. That will not only dump a lot of fructose on your liver, it will spike your blood glucose. This is pretty much the epitome of a highly processed food.

And note the ingredient list. There are five different kinds of sugar. (For a listing of the other names for sugar found on food labels, go here.)

Here is the label for Thousand Island salad dressing. Note that ingredient list. It’s off to a bad start with soybean oil, and it has a lot of stuff in it that looks like it came out of a lab rather than a plant or animal. That is a highly processed food.

A minimally processed food might look like this, Rao’s Homemade Marinara sauce. Notice that all of the ingredients are real food: tomatoes, olive oil, and spices.

And here is the nutrition label for the same product. Note that it has no added sugar (the sugar present is that from the tomatoes).

Be aware that similar products can have very different levels of processing.

Here are three different labels for bacon:

Great Value Hickory Smoked Bacon:

Yikes!

Applegate, Organic Hickory Smoked No Sugar Uncured Bacon:

Getting better. But they are being a little sneaky here. One of the criticisms of bacon is that many brands contain nitrates. But do you know what else has a lot of nitrates? Celery powder.

Wellshire Farms, Thick Sliced Dry-Rubbed Bacon:

Not too bad. Here we have just pork, salt, and minimal sugar.

Don’t assume that just because a food makes a health claim on the label or because it has a healthy reputation that it’s good for you. Likewise, don’t assume a food with a bad reputation is harmful. Always read the label.