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The Many flavors of Intermittent Fasting

Updated: Aug 21, 2021

There’s little evidence to suggest one form of IF(Intermittent Fasting) is better than another and no evidence suggesting IF is right for everyone (ask your registered dietitian for thoughts before diving in). Here’s a look at some common approaches.

Time- restricted fasting: Majority of the day is spent in the fasted state with specific hours allotted for eating. Popular methods include the 16:8 method (16 hours fasting: 8 hours eating) with ranges existing from a more liberal ratio (12:12) to pushing the limits of IF (20+:4).

Research on time-restricted fasting has found reductions in fasting glucose, and improvements in LDL- and HDL-cholesterol. Self-reported hunger was higher in the morning for those consuming a single meal per day, and subjects did not report becoming accustomed to this hunger over the course of the study.

Alternate- day fasting: Alternating between days of fasting (energy-free fluids only) and feasting (no rules).

Research comparing alternate day fasters to individuals on a standard, reduced-calorie diet found that there was no difference in weight loss or weight maintenance over the course of one year. Like time-restricted fasting, alternate day can lead to modest weight loss with possible improvement in metabolic parameters but hunger on fast days is intense and is unlikely to improve over time.

Modified fasting: Across the week, 5 days typical eating and 2, non-consecutive days of intake limited to 20 -25% of calorie needs.

Research suggests that this method results in weight loss, with modest and mixed effects on blood sugar control, blood lipid levels, and inflammatory markers. There is little evidence to suggest that this method produces superior weight loss or metabolic changes in comparison to standard energy restriction regimens.

Should You Try It?

IF is not the only (or even the best) way to lose weight but If food controls every minute of your waking hours and you’re desperate for a hard stop, then IF might be the break you need. Skip IF if you’re prone to overeating after periods of restriction. Individuals with diabetes, other chronic diseases, and (history of) eating disorder should ask their doctor before beginning IF. Athletes beware; research suggests that any form of fasting is likely detrimental to aerobic athletic gains since calories consumed in the hours before a workout are essential for optimal performance, recovery, and muscle gain.

Break the Fast Right

Choices during feasting hours and how you break the fast can make or break your success. Consider this; extended fasting may prompt the body to rely on ketones and endogenous fat stores for fuel once glycogen stores are exhausted. (And we know that followers of keto diets often turn to IF to jumpstart ketosis!). Relying on data from ketogenic dieters who broke their fast with simple sugars, we can theorize to uncover what happens to followers of IF who indulge in all-you-can-eat carbs when the feeding window finally opens. A small, recent study found that keto dieters who broke their ketosis with a bolus of 75 grams of simple sugar carbohydrate experienced vascular damage and inflammation suggesting that an influx of carbs after periods of fasting could push your health in the wrong direction.

To give yourself a break and ultimately move closer to health goals, plan ahead rather than eating everything in sight. Try easing back into eating with a ketogenic shakes or meals as your first choice. A keto or even a very low carb, high protein plate may better prevent an immediate blood glucose spike which can follow a plate full of mindless simple sugars. As your eating window continues, follow the advice of many fans of IF who report better progress when following a lower carbohydrate plan during eating hours.

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