In late April 2022 headlines were plastered across the internet calling for the death of intermittent fasting.
This was in relation to a New England Journal study out that week titled “Calorie Restriction with or without Time-Restricted Eating in Weight Loss”by Deying Liu, M.D. et al from Southern Medical University in Guangzhou, China.
I would have named it, “If you ask the wrong question, then you don’t get a helpful answer.”
The researchers asked if people lose more weight while on a calorie restricted diet in an 8 hour eating window versus the same calorie restriction, but no special eating window.
The rigorous study showed conclusive results that the narrow eating window wasn’t any better for weight loss than eating all day.
Women ate 1200-1500 calories and men 1500-1800 calories.
Both groups lost 14-18 pounds.
This was the question they wanted to answer, but it’s not the right question for most of us.
The problem with the study was the calorie restriction itself.
This eating style is a diet, and has long been blamed for yo-yo dieting.
People restrict calories for a set amount of time, then when they get tired of restricting, they eat more and regain the weight.
The number on the scale goes up and down, like a yo-yo.
Diets have long been blamed for yo-yo dieting. People restrict calories for a set amount of time, then when they get tired of restricting, they eat more and regain the weight. Click To Tweet
One of the most unhealthy issues with calorie restricted diets is that they promote the avoidance of healthy fats.
I think of it as the twisted sister of the 1980’s low fat craze that we now know to be unhealthy.
A person can eat a greater volume of food for the same calories if they avoid fats, so they are basically incentivized to avoid fat if they are restricting calories.
Healthy fats, like olive oil, avocados, and nuts are nutrient dense, and thus have more calories than other foods.
However they have important health benefits.
The olive oil you dribble on your salad will give you more calories than if you put on only vinegar, but olive oil is proven to decrease your chance of death from cardiovascular disease, cancer, and neurodegenerative diseases like Alzheimer’s.
So you’re avoiding a very healthy food in order to cut calories.
One of the most unhealthy issues with calorie restricted diets is that they promote the avoidance of healthy fats. I think of it as the twisted sister of the 1980’s low fat craze that we now know to be unhealthy. Click To Tweet
But can these healthy fats also help with weight loss?
An important hormonal model of obesity points to high insulin levels, often caused by insulin resistance, as causing more fat storage in human bodies.
Healthy fats do not increase insulin, so they are a helpful part of a weight loss eating plan in this model.
In fact, an eating plan that includes healthy fats decreases insulin levels and leads to both healthy and comfortable weight loss.
The body releases fat naturally with lower insulin levels.
Healthy fats do not increase insulin, so they are a helpful part of a weight loss eating plan in this model. In fact, an eating plan that includes healthy fats decreases insulin levels and leads to both healthy and comfortable weight loss. Click To Tweet
On the Harvard Healthy Eating Plate, meals ideally include protein (meat or beans), fiber (vegetables, fruits, whole grains), and healthy fats.
Consider the salad mentioned earlier.
If you choose to dribble on the olive oil, the healthy fat will help you feel full longer, so you wouldn’t feel hungry an hour afterwards.
Including healthy fats decreases the need for an insulin spiking snack between meals.
So eating the healthy fats aligns your hormones toward weight loss.
Healthy fats do not increase insulin, so they are a helpful part of a weight loss eating plan in this model.
But what does this have to do with intermittent fasting?
Doctors advising people on how to lose weight by decreasing their insulin levels are also suggesting intermittent fasting.
These doctors are not advising people to eat a calorie restricted diet.
So don’t give up your eating window just yet!
The good question I am hoping researchers will answer next: who loses the most weight?
Doctors advising people on how to lose weight by decreasing their insulin levels are also suggesting intermittent fasting.
Is it the human who eats three meals and no snacks that include protein, fiber, and healthy fats, or the human who eats two or three meals of that same formula in an 8 hour eating window?
I recommend people eat healthy fats, like olive oil, at all their meals for both a good healthy eating style and for weight loss.
We need more studies on intermittent fasting that do not include calorie restricted diets. I’m not giving up on intermittent fasting yet.
