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For decades, proponents of low carbohydrate (carb) eating have been saying that it’s the best choice for keeping blood glucose levels in range for people with diabetes, but the topic remains controversial.

Now, there’s a shift away from A1C as the gold standard for measuring glucose control to the more descriptive measurement of Time in Range (TIR). This provides new, clear evidence of how low carb eating benefits people with diabetes on a daily, weekly, and monthly basis.

This article will explore the relationship between low carb eating and TIR, and what that means to people with type 1 diabetes (T1D) in particular.

While there is no universal definition of what a low carb diet looks like, most healthcare professionals agree that “low carb” is considered fewer than 100 to 150 grams of carbs eaten per day.

This is much lower than the guidelines for most Americans that recommend carbohydrates making up between 45 percent and 65 percent of a person’s total daily calories.

If a person eats a typical 2,000-calorie-per-day diet, that equals between 225 and 325 grams of carbs per day.

There are many different ways to go about restricting your carb intake. Some extremely low carb diets include the ketogenic diet as well as the paleo diet, where people typically eat fewer than 50 grams of carbs per day.

Other popular low carb diets include the Atkins diet, which eliminates virtually all carbs, as well as the South Beach diet and some versions of the Mediterranean diet, that limit carbs from grains, instead focusing on carbs found naturally in fruits and vegetables.

A popular choice among people with diabetes is the so-called Bernstein diet, an ultra-low carb approach pioneered by Dr. Richard Bernstein, who lives with T1D himself. This method advocates eating full fat, mostly animal products, and limiting carbs to 20 grams or fewer per day.

The eating patterns of Americans have taken a drastic turn away from the lower fat, higher carbohydrate diets of the 1970s and 1980s to higher fat, lower carb diets popular today.

The low fat food trend was borne out of scientific studies from the 1940s, that correlated high fat diets with higher rates of cholesterol. That suggested to physicians at the time that promoting a low fat diet might help prevent the rising rates of heart disease affecting the nation.

But when the fat content of foods was reduced, sugar was added to make up the difference in taste, resulting in a plethora of low fat, higher carb foods in grocery stores, including reduced fat ice-cream, cakes, cookies, pies, and many other desserts and treats.

That eating trend spread, even though no evidence ever surfaced that eating a low fat diet prevented heart disease or promoted weight loss.

It’s only been within the last 15 years that solid evidence has become widely available showing that low carb foods that are high in healthy (plant) fats do not increase the likelihood of heart disease, and instead can promote rapid weight loss, treat obesity, and even improve blood sugars in people with diabetes.

A 2020 survey by the International Food Information Council found that 7 percent of Americans self-reported eating a low carb diet, up from 5 percent in 2018, and that trend continues to rise.

People with diabetes are forever plagued with walking the tightrope of blood sugar management: balancing insulin, carbs eaten, exercise, stress, sleep, hormones, work, and other activities while constantly monitoring and manually controlling their defunct pancreases.

Eating large amounts of carbs can complicate this delicate balance, because higher amounts of carbs will spike blood sugar in the short term, and require a larger amount of insulin in the bloodstream to offset the impact. This can lead to increased risk of hypoglycemia (dangerous low blood sugar) and the “rollercoaster” of glucose highs and lows that can sometimes follow.

In the past, people with diabetes and their healthcare teams had only one way to assess their glucose control: the A1C test, which provides a mathematical average of blood sugar levels over the past 3 months. The A1C provides zero insight into how a person’s blood sugar may be fluctuating on a daily or weekly basis or in response to behavior patterns.

Now, the shift towards focus on TIR is helping to provide much more insight. TIR literally measures how much time in a day a person is staying within a healthy blood sugar range (typically between 70 to 180 mg/dL).

Your TIR measurement is a percentage of the day or week or month that you remain within said range — so for example, a TIR of 77 for last week would mean that you stayed within the desired glucose range for 77 percent of the time during the past 7 days.

This measurement requires a continuous glucose monitor (CGM) system that will tally the exact amount of time in a day that a person is staying within their desired range.

The push towards elevating TIR has become extremely popular, with celebrities like pop singer and actor Nick Jonas kicking off a Time in Range Initiative to promote TIR to patients across the country as one of the best “powerful metrics for modern diabetes management.”

Experts agree that TIR provides a far better picture of actual diabetes management, as the traditional A1C can hide a string of super high and super low blood sugars, by simply providing an average number derived over the past 12 weeks.

Now, people with diabetes who have found that eating a lower carb diet helps them maintain lower and steadier glucose levels no longer have to rely on anecdotal clues. Their TIR results show solid evidence that low carb eating makes diabetes management easier, due to both fewer carbs in their system (preventing hyperglycemia), as well as much less insulin in their bloodstream (helping to prevent hypoglycemia).

This can be very powerful for individuals with diabetes to celebrate their success.

There is some clinical research providing evidence that eating an extremely low carb diet improves insulin sensitivity by 75 percent, as well as improving blood sugar levels. But the medical establishment has been historically slow to endorse low carb eating.

Now, TIR is clearly illustrating that with lower carb intake (and thus fewer variables to manage) blood sugar spikes or drops are less frequent and more predictable.

Many people with diabetes see great success with eating a low carb diet.

Kyle Murray, a registered dietitian and certified diabetes care and education specialist (CDCES) from Queens, New York, says, “I’ve had a lot of blood sugar success eating between 30 to 60 grams of carbohydrates per day. It’s the ‘rule of small numbers’ the Dr. Bernstein followers talk about. No big carbs, no big doses, no big highs, no big lows. Huge quality of life improvement.”

Keith Fischer, who lives with T1D in San Diego, California, says, “I’ve done the keto diet and low carb, and both work significantly better for me than the standard American diet. There is no pre-bolus timing or guesswork for when a spike will hit.”

Another person who has had immense success with low carb eating is Joshua Reese, who lives with T1D in Knoxville, Tennessee. He says, “[Low carb eating] is not for everyone, but I do enjoy more savory foods. Lots of salads, meats, cheeses, and nuts. There are so many resources online for low carb food substitutions. I eat about 75 carbohydrates per day. I promise I still know that carbs are delicious and not the devil, this is just the right choice for me.”

He continues, “My time in range [pre-low carb] was only ever around 70 percent, but my time in range has increased up to 90 percent since eating low carb.”

Erica Montoya, who works in public health and lives in Allentown, Pennsylvania, says, “I love eating low carb to manage my blood sugars. My time in range is the best it’s ever been, and I feel healthier not eating so many added sugars in my diet. I’ve found that eating low carb is easier in the summertime, when there’s lots of fresh vegetables for salads available at farmers markets and in the grocery store.”

However, some people struggle to maintain a low carb diet, for understandable reasons.

Joe Wotawa, who was recently diagnosed with diabetes and lives in Wyoming, tried the paleo diet and says, “It involved unpredictable, life threatening low blood sugars more than once per month. It also increased both my cholesterol and blood pressure. I did not enjoy that.”

Tim W. from St. Louis, Missouri, adds, “I struggle to eat low carb consistently when my family is not low carb. My best diabetes days are days when my family is busy and everyone needs to fend for themselves, but my best family days are not my best diabetes days.”

Kevin M., a nurse from Albany, New York, couldn’t sustain his energy with a low carb diet. “Working 12-hour shifts in the emergency department and eating under 20 grams of carbohydrates per day left me completely burnt out and sluggish. I’ve since increased my daily carbohydrate intake to around 70 to 80 and feel 100 percent better.”

Many people with diabetes have found a lot of success with eating a low carb diet, including improved A1C levels and TIR, lower insulin and other diabetes medication requirements, fewer blood sugar fluctuations, and even sustained weight loss.

However, the diet can be hard to sustain, and some people experience negative side effects such as constipation, fatigue, and chronic micronutrient deficiencies if eating extremely low carb for long stretches at a time.

Always work with your doctor to make the best decision for you, your body, your lifestyle, and your health goals.

Experiment and see what success looks like for you. If you have access to a CGM, then using TIR is a powerful way to measure your success.

Perhaps you’ll thrive on a low carb diet, or you may find that your body needs more carbs to really feel at its best.

As Ariel H. of Grand Rapids, Michigan, has found: “I’ve oscillated between low fat, higher carb, and low carb, higher fat diets before, and I currently find myself squarely in the middle,” she says. “I’m enjoying healthy foods I like without the guilt, and indulging every once in a while. It works best for me.”