Is this popular health trend right for you?
Most of us consider making healthier lifestyle changes at the beginning of the year, and variations on weight loss and better eating are always popular. One concept receiving attention in recent years suggests when you eat is as important as what you eat. Intermittent fasting, a modern variation on an ancient way of life, can be a game-changer for many, but a bad choice for others.
This is the first article in a series that will be evaluating the hottest health and longevity trends.
How It Works
Intermittent fasting, sometimes called cyclic fasting, describes an eating schedule that includes avoiding food for short periods in order to improve your overall health. While variations exist, all limit eating during specific time periods so your body can heal and recover. Is it something you should try in the new year?
This approach to eating has many well-documented upsides, such as helping with weight loss, disease prevention, and better hormone regulation. People who’ve tried it say it’s easier to stick to than counting calories or restricting certain foods. Intermittent fasting isn’t right for everyone – and talking with a doctor before making any major lifestyle change is always smart – but the body of research shows it’s generally safe and effective when combined with healthful, sensible food choices. It also may be more closely suited to how our bodies were designed to work.
We’ve all grown up eating breakfast, lunch and dinner, but that wasn’t how our earliest ancestors lived. If a hunt or forage was unsuccessful, they might not eat at all that day. Our modern world has food available on demand from our kitchen pantries, 24/7 supermarkets, and Doordash deliveries, but these conveniences also include a lot of carb-heavy processed foods full of sodium and high-calorie refined grains and sugars. A diet like this takes a toll on us.
Immediately after we eat, our bodies go into a fed state and process what we’ve consumed. We store energy, usually as fat, and insulin and blood sugar levels rise, overpowering our other hormones. Only after a few hours do we move into a fasting state, when our system burns that stored energy. With regular meals and constant snacking, we don’t stay in a fasting state for long, if at all, and that extra energy – again, largely fat – hangs around. Sustained food breaks of 12 hours or more can give our bodies the rest they need.
Skipping food for 12 consecutive hours or more may sound tough, but you can pass a lot of that time while you sleep at night. Sleeping hours mark the longest daily fast for most of us and breaking that fast is how the morning meal got its name. If you finish dinner before 7 p.m., get a reasonable night’s sleep and then don’t eat again until 7 the next morning, that’s already a 12-hour fast. Earlier dinners and later breakfasts – or skipping breakfast altogether – further stretches this fasting window. It’s a good idea to avoid eating after dinner anyway, as late-evening snacks not only tend to be empty calories, but we also burn them slower. Intermittent fasters say compressing your eating schedule isn’t as hard as it sounds, and it becomes easier the more you do it. A benefit of this adjustment is that your body produces less ghrelin, the hormone that makes you feel hungry.
On a fasting plan, the meals you do eat should include all the essential nutrients. That’s why sensible food choices and hydration are key to this approach. Your body processes vegetables, whole grains, clean proteins and other good-for-you foods – along with the occasional treat – more efficiently than a steady intake of pizza, burgers and ice cream. If you’re not currently a healthy eater, experts recommend improving your diet before you try fasting. Otherwise, you may be more tempted to finish a fast with a junk food binge.
Varieties of Intermittent Fasting
Most fasting regimens fall into one of three categories, with the biggest differences being the lengths and frequencies of the fasting period.
- Time-Restricted Feeding limits your eating to a 8-to-12-hour window and you fast the rest of the time. A 12-hour eating window, as in the example above, can be a good approach for first-timers. If they do well, they can try stretching the fast to 16 hours.
- Alternate-Day Fasting involves one day of normal, healthy eating, followed by one day of taking in less than a fourth of your usual calories. A 2,000-calorie eater would cut down to 500 or less every other day. This is the most-studied type of intermittent fasting, but it’s also more difficult to maintain over the long term.
- 5:2 Fasting is a variation of alternate-day fasting where you eat normally for five days each week and cut way back for the remaining two 24-hour periods, as long as they’re not consecutive days.
Potential Health Benefits
So what are the upsides of skipping these meals? Extensive research shows many positive effects can come from combining sensible eating and intermittent fasting.
If you want to lose weight and belly fat, intermittent fasting has a track record of success. Reviews of studies find fasters can lose as much as 10 percent of their body weight, even those who didn’t start out obese. Fasting also helps our body release human growth hormone and norepinephrine, which burns fat quicker while preserving muscle. That’s why intermittent fasting may be a good strategy for athletes in non-endurance sports.
Resting our bodies during fasts also appears to benefit the brain. Lab rodents fed intermittently had better motor coordination and learning response, with less of the oxidative stress associated with normal age-related brain changes. Other studies found fasters improved their verbal memories, short term memories, high-level executive function and overall cognitive function. Intermittent eating schedules can also reduce neuroinflammation, a factor in Alzheimer’s disease and depression.
Intermittent fasting can also promote a healthy heart by lowering cholesterol and triglycerides. Researchers found an overall 20 percent cholesterol reduction among intermittent fasters they studied, with much of it coming from LDL, so-called “bad cholesterol.” Fasting also lowers other heart disease risk factors and increases levels of adiponectin, helpful in preventing cardiovascular disease and heart attack.
Giving your body breaks from intensive insulin processing can help reverse insulin resistance, a way for adults to manage prediabetes or type-2 diabetes without expensive medications. In one study, fasters saw insulin levels drop by as much as 57 percent. Time-restricted feeding with a fasting window of 16 hours or more has been shown to prevent blood sugar spikes and crashes and improve overall insulin sensitivity.
Inflammation, your immune system’s response to a wound or illness, is helpful in short spurts, but chronic inflammation is associated with cancer, diabetes, arthritis, and heart disease. New research finds intermittent fasting reduces markers associated with this chronic inflammation. One study conducted during Ramadan found Muslims who followed daytime fasts saw their inflammation levels decline at the same time.
Fasting puts our cells under mild stress and, in this case, what doesn’t kill them makes them stronger. This stress, like exercise, better equips our cells to fight stress and disease. Fasting also appears to cause cells to start eliminating their own damaged or dysfunctional elements. This cleaning process, autophagy, has been linked to better protection against cancer, dementia and other diseases.
Not for Everybody
While intermittent fasting is generally safe, it can do more harm than good for some people.
- People with type 1 diabetes who take insulin may find fasting leads to dangerous hypoglycemia. In addition, people with HPA-axis dysfunction may not do well with the additional cortisol that fasting produces. Hormone balance changes can also cause issues for people with thyroid problems. Those with gallstones may find it can make existing gallbladder problems worse. At the very least, check with your doctor.
- Experts strongly discourage pregnant and breastfeeding people from fasting because it could deprive both them and their baby much-needed nutrients. It’s also good to avoid fasting if you’re trying to maximize fertility during ovulation.
- Endurance athletes, such as marathoners and triathletes, should probably avoid fasting because studies have shown it can have a negative effect on their performance.
- People with eating disorders and low body weight may not respond well to intermittent fasting.
- The vast majority of research promoting fasting’s benefits has been performed on adults, but little data exists on its effects on young children and seniors.
Intermittent fasting may not fit your lifestyle if you struggle with stress or have inconsistent daily schedules. Parents with young children may find it difficult to balance their own eating programs with their little ones’ appetites. Finally, some people who try fasting decide they don’t like how periods without food made them feel – a good example of following your body’s advice.
The Bottom Line
If you’re looking at lifestyle changes, intermittent fasting has enough evidence-backed benefits to justify consideration. Rescheduling meals can take getting used to, but many find it a more viable long-term solution than traditional diets. At the very least, understanding how our bodies process food may convince us to make healthier choices and curb snacking, which can do a lot of good on its own.