Intermittent Fasting for Weight Loss & Longevity: How to Lose Fat and Age Well
Learn how intermittent fasting can be a sustainable and healthy way to lose weight and increase longevity
You may not be chasing a number on the scale anymore.
What you want now is consistent energy, mental clarity, strength, and the ability to move through life without pain or constant fatigue. You want to age well — not just live longer, but remain resilient, capable, and engaged as the years pass.
And yet, for many adults, weight gain, metabolic changes, and declining vitality seem to arrive quietly with age, even when they believe they are “doing everything right.” This experience is no longer the exception. Today, adults considered to be at a healthy weight are in the minority, and metabolic dysfunction has become increasingly common across all age groups. Over the past two decades alone, the average adult has gained weight steadily, reflecting deeper shifts in how our bodies process energy, stress, and nutrition.
These changes are not merely cosmetic. Excess weight and impaired metabolic health are closely linked to conditions we associate with aging, including type II diabetes, cardiovascular disease, neurodegenerative disorders, and certain cancers. In this context, weight loss is not about aesthetics — it is about long-term health, disease prevention, and longevity.
Intermittent fasting has gained attention in recent years, often framed as a trend or weight-loss strategy. But when stripped of hype, fasting is not a diet at all. It is a metabolic intervention that influences insulin sensitivity, mitochondrial function, inflammation, and how efficiently the body accesses stored energy.
When used appropriately, intermittent fasting can support fat loss, metabolic flexibility, brain health, and healthy aging. When used incorrectly — especially without regard for hormones, stress physiology, sleep, or blood sugar regulation — it can be ineffective or even counterproductive.
In this article, we’ll explore what intermittent fasting actually is, how it works in the body, who it may benefit, and when a personalized, root-cause approach is essential — particularly for women.
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What Is Intermittent Fasting?
Simply put, intermittent fasting is a length of time spent without eating. Although we put it in the diet category, it's not about what you eat but when you eat. People who participate in intermittent fasting most often don’t change the type of food they eat, but shorten the windows of time spent eating and lengthen the windows of time spent fasting.
Although intermittent fasting has gained popularity in recent years, it’s not a new practice. In fact, when humans spent most of their time hunting and gathering they would go long periods of time between meals.
Many religious practices include fasting as part of their religious practices. Buddhists, Christians, and Muslims all include fasting as a way to prepare for specific religious ceremonies or during specific times of the year.(2)
Outside of religious practices, most people who participate in intermittent fasting do so following one of these methods:
Alternate-Day Fasting
Alternate-Day Fasting is fasting for one day (eating <500 calories) and eating regular meals on alternate days.
5:2 Fasting
5:2 Fasting is where you eat your regular diet for five days and then fast for the remaining two days, eating <500 calories on each of your fasting days. A variation of the 5:2 diet is fasting for two days of the week, but the days are not consecutive.
Time-Restricted Eating
Time-Restricted Eating refers to a period of time during the day when you're allowed to eat. This is often an eight-hour window where you consume your calories of unrestricted foods and then fast for the remaining 16 hours.
Recent studies suggest the current window of time most humans eat is 14.5 hours. The biggest difference between time-restricted eating and intermittent fasting for weight loss is that time-restricted eating is aligned with the biological day as compared to intermittent fasting which implies fasting for a 24-hour period or longer.(2)
How Intermittent Fasting Supports Weight Loss
Intermittent fasting helps you lose weight by allowing time for your body to burn through the calories you’ve eaten and allows for time to burn fat as an alternate energy source.
When you eat regular meals and snacks throughout the day, your body is taking in a regular supply of energy. Calories are converted into sugar to fuel the body. When your body no longer needs fuel to function the excess sugar is then stored as fat.
Intermittent fasting allows the body time to burn off excess sugar and switch to burning fat as an alternate fuel source helping you to lose weight and improve your body composition. This process is called metabolic switching.(3)
Understanding whether your body can efficiently make this metabolic shift requires deeper insight into insulin sensitivity, mitochondrial function, and stress physiology.
→ Advanced Functional Lab Testing
So what does this all mean? A 2019 review of 11 randomized controlled studies found most overweight and obese people who participated in the form of intermittent fasting had a weight loss of 3-8% of their total body weight.(4)
But this is not the only benefit of intermittent fasting.
The Health Benefits of Fasting Beyond Weight Loss
More and more research suggests the benefits of intermittent fasting go beyond weight loss and help prevent or reverse diseases commonly seen with aging.
Type II Diabetes
Type II Diabetes occurs when your body is unable to burn excess glucose found in the body. Intermittent fasting helps to stimulate the insulin receptors in the body, helping your muscles and liver burn the added glucose. Having excess glucose in the body can also contribute to added inflammation found in the body which puts more stress on other systems of the body, including the brain, liver, and the heart.
Cardiovascular disease
Cardiovascular disease includes symptoms like high blood pressure, high cholesterol, poor heart rate, and insulin resistance. These symptoms not only can cause heart disease but also increase your risk of stroke. Intermittent fasting has been shown to lower blood pressure, improve your heart rate, enhance your physical fitness, and lower your cholesterol.
Neurological disorders
Neurological disorders, including Alzheimer's Disease, Parkinson's Disease, and stroke, are all thought to have impaired mitochondrial function within the cells of the body. In a previous blog, Why Boosting Your Mitochondrial Function is the Key to Living a Long and More Vibrant Life, I go in-depth talking about how mitochondrial function relates to aging and dis-ease.
Intermittent fasting helps to protect our cells against oxidative stress and damage to the mitochondria delaying and potentially preventing the onset of neurological diseases like Alzheimer’s.
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Traumatic injuries
Traumatic injuries, including spinal cord injuries and peripheral neuropathy, have been shown to benefit from intermittent fasting when practiced prior to an injury and continued after an injury. Some studies show improvements in overall nerve conduction and a reduction in spinal cord lesions. In short, intermittent fasting helps healing following an injury.
Cancer prevention
Intermittent fasting and periodic fasting (fasting for 2 days or more) have been shown to be as effective as chemotherapy. And decrease the widespread of specific cancers. Intermittent fasting also can protect normal cells from the toxic effects of chemotherapy treatments.
The potential benefits of intermittent fasting are profound. And there continues to be emerging evidence demonstrating its benefits related to cancer prevention and multiple sclerosis.(5)
Is Intermittent Fasting Safe for Everyone?
Intermittent fasting is not for everyone. Children and teens under the age of 18 years old should not participate in fasting.
Women who are pregnant or breastfeeding, people who have type I diabetes, and those who have a history of eating disorders should not practice intermittent fasting.
→ Women’s Hormone & Reproductive Health
For women, the phase of your cycle is also an important factor to keep in mind. (6)
And you should always consult with your healthcare provider to discuss if intermittent fasting is right for you.(7)
Some side effects you may experience include:
Hunger
Fatigue
Insomnia
Irritability
Decreased concentration
Nausea
Constipation
Headaches
For most people, these side effects go away within one month. And the benefits of intermittent fasting far out way momentary discomfort. But this is also why I recommend you talk with your doctor when starting a new health routine.(8)
A Root-Cause Approach to Weight Loss at Denver Sports & Holistic Medicine
With the sheer volume of weight-loss advice available today, knowing where to begin can feel overwhelming. Diet strategies come and go, but lasting weight loss rarely comes from a single intervention. Sustainable change requires understanding why the body is holding on to weight in the first place.
At Denver Sports and Holistic Medicine, Dr. Martina Sturm partners with patients using a comprehensive, root-cause approach to weight loss and metabolic health. Care begins with a detailed review of your health history, lifestyle patterns, stress load, sleep quality, and metabolic function to understand what has—and has not—worked for you in the past.
When appropriate, advanced functional lab testing is used to identify underlying contributors to weight gain and metabolic resistance, including hormonal imbalances, disrupted sleep-wake rhythms, food sensitivities, chronic stress, impaired detoxification pathways, and gut health dysfunction.
From there, Dr. Martina develops a personalized plan designed to support long-term metabolic health and resilience. This may include targeted nutrition and lifestyle strategies, evidence-based supplementation and herbal medicine, acupuncture for nervous system regulation and metabolic support, and other therapies when clinically indicated.
Intermittent fasting, when used, is never prescribed in isolation. It is carefully tailored based on hormones, metabolic flexibility, nervous system balance, and lab findings to ensure it supports—rather than stresses—the body.
If you’re ready for a thoughtful, individualized approach to weight loss that prioritizes health, longevity, and sustainability, you’re invited to take the next step.
Request your free 15-minute consultation with Dr. Martina Sturm
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FAQs: Intermittent Fasting, Weight Loss & Longevity
What is intermittent fasting, and how is it different from a diet?
Intermittent fasting focuses on when you eat rather than what you eat. It involves structured periods of eating and fasting that allow the body to burn through stored glucose and shift toward using fat as fuel. Unlike traditional diets that restrict specific foods, intermittent fasting works by supporting metabolic flexibility, insulin sensitivity, and cellular repair processes.
Does intermittent fasting help with weight loss?
Intermittent fasting can support weight loss by lowering insulin levels, improving the body’s ability to access stored fat, and reducing metabolic resistance. Many people experience gradual, sustainable fat loss when fasting improves underlying metabolic function rather than simply reducing calories.
Is intermittent fasting safe for everyone?
Intermittent fasting is not appropriate for everyone. It may be unsafe for children, individuals who are pregnant or breastfeeding, those with type I diabetes, a history of eating disorders, or certain hormonal or metabolic conditions. Fasting should always be approached thoughtfully and personalized to the individual.
How does intermittent fasting affect women differently?
Women’s hormones are closely tied to blood sugar regulation, stress physiology, and circadian rhythm. Poorly timed or overly aggressive fasting can disrupt menstrual cycles, worsen fatigue, or increase stress hormones. For many women, fasting must be adapted based on cycle phase, metabolic health, stress load, and sleep quality.
Can intermittent fasting support longevity and healthy aging?
Intermittent fasting may support longevity by improving insulin sensitivity, reducing chronic inflammation, enhancing mitochondrial function, and activating cellular repair pathways such as autophagy. These mechanisms are associated with reduced risk of age-related metabolic, cardiovascular, and neurological conditions.
What is metabolic switching, and why does it matter?
Metabolic switching refers to the body’s ability to shift from using glucose to using fat for energy. Intermittent fasting encourages this transition by allowing insulin levels to fall. Poor metabolic flexibility is common in insulin resistance and is often associated with weight gain, fatigue, and chronic disease.
Can intermittent fasting improve blood sugar regulation?
When used appropriately, intermittent fasting can improve insulin sensitivity and reduce excess circulating glucose. This can be beneficial for individuals with insulin resistance or early metabolic dysfunction. However, fasting without understanding blood sugar patterns can sometimes worsen symptoms, making individualized guidance important.
Are side effects normal when starting intermittent fasting?
Some people experience temporary symptoms such as hunger, fatigue, headaches, irritability, poor sleep, or difficulty concentrating. These effects often improve as the body adapts. Persistent or worsening symptoms may indicate that fasting needs to be modified or avoided.
Is lab testing helpful before starting intermittent fasting?
Functional lab testing is not always required, but it can provide valuable insight, especially when weight loss has been difficult or symptoms are present. Testing may reveal insulin resistance, hormonal imbalances, thyroid dysfunction, stress hormone patterns, or nutrient deficiencies that influence how the body responds to fasting.
Is intermittent fasting enough on its own for long-term weight loss?
Intermittent fasting is rarely effective as a standalone strategy. Sustainable weight loss typically requires a comprehensive approach that addresses nutrition, sleep, stress, hormonal balance, gut health, detoxification capacity, and nervous system regulation. Fasting is most effective when used as part of a personalized, root-cause plan.