IF as a weight loss approach has been around in various forms for ages, but was highly popularized in 2012 by BBC broadcast journalist Dr. Michael Mosley’s TV documentary Eat Fast, Live Longer and book The Fast Diet, followed by journalist Kate Harrison’s book The 5:2 Diet based on her own experience, and subsequently by Dr. Jason Fung’s 2016 bestseller The Obesity Code. IF generated a steady positive buzz as anecdotes of its effectiveness proliferated.
Based on this, researchers from the University of Alabama conducted a study with a small group of obese men with prediabetes. They compared a form of intermittent fasting called “early time-restricted feeding,” where all meals were fit into an early eight-hour period of the day (7 am to 3 pm), or spread out over 12 hours (between 7 am and 7 pm). Both groups maintained their weight (did not gain or lose) but after five weeks, the eight-hours group had dramatically lower insulin levels and significantly improved insulin sensitivity, as well as significantly lower blood pressure. The best part? The eight-hours group also had significantly decreased appetite. They weren’t starving.
IF makes intuitive sense. The food we eat is broken down by enzymes in our gut and eventually ends up as molecules in our bloodstream. Carbohydrates, particularly sugars and refined grains (think white flours and rice), are quickly broken down into sugar, which our cells use for energy. If our cells don’t use it all, we store it in our fat cells as, well, fat. But sugar can only enter our cells with insulin, a hormone made in the pancreas. Insulin brings sugar into the fat cells and keeps it there.
Jerimiah, the linked study in the article (https://www.sciencedirect.com/science/article/pii/S1550413118302535) specifically studied “eTRF”(Early Time-Restricted Feeding) from 8am – 2pm, and implies that eating earlier is better than later. I haven’t read the study (it’s behind a damn Elsevier pay-wall), so I don’t know how strongly they feel about early vs late, though. For me, personally, 12-8 is doable, and skipping dinner (given the existence of a family and the desire to have dinner with said family) isn’t doable, so I’m pleased to hear from you and April above that it’s working. Just starting!
To encourage ketone production, the amount of insulin in your bloodstream must be low. The lower your insulin, the higher your ketone production. And when you have a well-controlled, sufficiently large amount of ketones in your blood, it’s basically proof that your insulin is very low – and therefore, that you’re enjoying the maximum effect of your low-carbohydrate diet. That’s what’s called optimal ketosis.
AN IMPORTANT CAVEAT: Intermittent Fasting can be more complex for people who have issues with blood sugar regulation, suffer from hypoglycemia, have diabetes, etc. If you fit into this category, check with your doctor or dietitian before adjusting your eating schedule. It also affects women differently (there’s a whole section dedicated to that here).

This principle involves eating low-energy-dense foods and can help you lose weight by feeling full on fewer calories. Healthy choices in each of the other food groups in moderate amounts make up the rest of the pyramid — including whole-grain carbohydrates, lean sources of protein such as legumes, fish and low-fat dairy, and heart-healthy unsaturated fats.
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