How Time-Restricted Eating May Lower  Heart Disease, Type 2 Diabetes Risk

• In the United States, an estimated 1 in 3 people have metabolic syndrome, which raises the risk for developing type 2 diabetes and heart disease.
• A new study investigates whether a form of intermittent fasting called time-restricted eating (TRE) might help remedy the condition.
• While more long-term studies are needed, the researchers found significant improvements after following a short-term personalized TRE regimen.

Intermittent fasting protocols are gaining interest among researchers and health enthusiasts for their potential benefits.

A new study, published in the Annals of Internal Medicine, examined the effects of time-restricted eating (TRE), a form of intermittent fasting (IF) in people with metabolic syndrome.

The researchers found that eating within an 8–10-hour window may help improve blood sugar control in people with the condition. Although the study has some limitations, its findings align with previous, similar research.

Health effects of time-restricted eating

According to the authors of the new study, one-third of people in the United States have metabolic syndrome, an umbrella term for a cluster of cardiovascular risk factors: 

• high blood pressure
• high blood sugar levels
• excess fat around the waist
• high triglyceride (blood fat) levels
• low levels of good cholesterol (HDL)

If left untreated, people with metabolic syndrome have an increased risk of developing diabetes and heart disease. 

Uncovering lifestyle interventions to reduce the burden of metabolic syndrome is vital work for researchers. Some scientists believe that time-restricted eating (TRE) might help people with this condition.

Following a TRE protocol means only consuming calories for a set number of hours each day. Outside of these times, only water or black, unsweetened tea and coffee may be consumed.

As an example, if someone starts their breakfast at 9 a.m. and finishes their last meal of the day at 9 p.m., they have a 12-hour eating window. If they decided to try TRE, perhaps they would skip breakfast, eat their first meal at midday, and eat their final meal at the same time as usual. This would give them a 9-hour eating window.

Previous research has linked TRE with:

• improved blood sugar control in people with diabetes
• decreased blood pressure
• weight loss
• lower blood fat levels

Can time-restricted eating treat metabolic syndrome?

The latest study is a randomized controlled trial — the gold standard of medical research. The scientists recruited 108 people with metabolic syndrome and an average age of 59.

For the 3-month study, the researchers split the participants into two groups:

• nutrition counseling
• nutrition counseling plus a personalized 8- to 10-hour TRE intervention.

At the beginning of the study, participants’ average eating window was just over 14 hours. During the study, they reduced their eating window by around 4 hours.

At the end of the study, the TRE group had significantly improved their HbA1c, or hemoglobin A1C, which is a marker of average blood sugar levels used to monitor diabetes.

“Lowering HbA1c reduces the risk of type 2 diabetes,” Adrian Hernandez, a registered dietitian nutritionist and owner at AEH Nutrition LLC, who was not involved in the study, told Healthline. “By reducing the risk or progression of type 2 diabetes, you also improve the development of metabolic syndrome.”

Those in the TRE group also lost weight without losing muscle mass, reduced their body mass index (BMI), and lost belly fat, all of which can reduce the risk of chronic disease if maintained.

Although the results are hopeful, the authors note that the study was relatively short duration, and that they had to rely on participants reporting when they ate — which is not always reliable. 

“While there are clear limitations to the study, I would still say TRE is a viable option for those with metabolic conditions,” Hernandez said, noting that other “research on TRE and intermittent fasting shows similar outcomes.”

How does time-restricted improve metabolic health?

Rebecca Russell, a functional medicine registered dietitian at The Social Nutritionist, not involved in the study, explained how TRE can help people with metabolic syndrome.

“One reason TRE may be effective is that it aligns food intake with the body’s natural circadian rhythm,” she told Healthline.

Circadian rhythms help orchestrate the rise and fall of hormone levels throughout the day, sleep-wake cycles, metabolism, digestion, and much more.

“By restricting eating to an 8–10 hour window, we can work with our body’s natural ebb and flow, enhancing metabolic efficiency,” Russell continued.

Russell explained how eating when the body is naturally primed for digestion and energy utilization may help improve:

• blood sugar regulation
• lipid profiles
• overall metabolic health

Avery Zenker, a registered dietitian at EverFlex Fitness, not involved in the study, noted how TRE might help in other ways. “Fasting periods also give the digestive system a break, which can improve gut health and allow for essential repair and recovery,” Zenker told Healthline.

Mir Ali, MD, a board-certified bariatric surgeon and medical director of MemorialCare Surgical Weight Loss Center at Orange Coast Medical Center in Fountain Valley, CA, not involved in the current study, told Healthline that, other than circadian alignment, “fasting for a period of time directs the body toward burning fat.” This helps explain the weight loss seen in this and other studies, Ali noted.

Food quality matters

If you are eating less food overall, it is important to focus on quality to ensure you get all the essential nutrients your body needs during your eating window.

“Choosing the right foods is the most important thing for weight loss,” Ali said.

Zenker agreed. “TRE cannot compensate for low-quality food choices, so it’s important to focus on eating a variety of nutrient-dense foods rather than relying on timing alone to improve health outcomes. Focusing on a nutritious diet is essential, regardless of when you’re eating,” Zenker said.

Who should avoid time-restricted eating?

According to Hernandez, TRE is not suitable for everyone, including:

• pregnant people
• malnourished individuals
• anyone taking medications that affect blood sugar
• athletes or very active individuals who have higher nutrient needs

Also, “Individuals with a history of disordered eating may find the restrictive eating window triggering, potentially exacerbating unhealthy behaviors,” Russell said.

“Additionally,” she continued, “people with type 1 diabetes or those on medication for type 2 diabetes need to be cautious as fasting can lead to dangerous drops in blood sugar.”

How to get started with TRE

Russell stressed the importance of consulting with a “qualified healthcare professional to determine if TRE is suitable for your individual needs. If you decide to proceed, a gradual approach is often best.”

She suggests first reducing your eating window to 12 hours, then gradually dropping it down to 10, and finally 8 hours. “It’s crucial to maintain a balanced, nutrient-dense diet within your eating window.”

“If you tend to eat close to bedtime, I’d start there first,” Zenker said. “Eating closer to bedtime is linked to poorer health outcomes, so cutting out late-night snacks is a positive start.

Another tip Zenker shared is to “eat an adequate amount of protein and fiber since this can help manage hunger and satiety during the fasting period. And don’t forget to prioritize other lifestyle factors, like sleep, stress, and exercise”.

Importantly, Russell explained, “If you find yourself overeating or reaching for less nutritious foods due to excessive hunger during your restricted eating window, TRE may not be the healthiest approach for you.”

Takeaway

A new study concludes that restricting food intake to 8–10 hours each day might reduce metabolic syndrome, potentially reducing cardiovascular risk. 

Although TRE might be beneficial for some, it is still important to concentrate on food quality. Importantly, certain people should not try TRE, like those who are pregnant or have diabetes.

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