Is Fasting Beneficial for Weight Loss?


“Is Fasting Beneficial for Weight Loss?” Fasting obviously causes consistent,
dramatic weight loss, but how do fasted
individuals do long-term? Some research groups reported
extremely disappointing results. Here’s what they saw. Average subject started out
at about 270 pounds and, in the six months before the
fast, continued to gain weight as obese persons tend to do. Then, after 24 days of what they
called “inpatient starvation,” a dramatic 27-pound weight loss. Then, what do you think happened? They gained it all back and more, though one could argue
if they had not fasted they might have been up
around here at that point. In another study with follow-ups
ranging up to 50 months, only 4 out of 25 so-called
“superobese” patients achieved even partial sustained success. Based on these kinds of data some
investigators concluded that “complete starvation is of no value in the long-term treatment
of obese patients.” Other research teams reported
better outcomes. One series of about 100 individuals
found that 60% either retained at least some weight loss at
follow-up or even continued losing. The follow-up periods varied from
1 to 32 months with no breakdown as to who fasted how long, though,
making the data hard to interpret. One year after fasting, 62 patients
down 16 pounds in 10 days. In another study, 40 percent retained at
least 7 pounds of that weight loss. Put six such studies together
and hundreds of obese subjects fasted for an average of 44 days,
lost an average of 52 pounds, and around one or two years later 40%
retained at least some of the weight loss. So, most gained all
their weight back, but 40 percent is extraordinary
for a weight loss study. Follow 100 obese individuals getting
treated at a weight loss clinic with a standard low-calorie diet… and researchers found only 1 out of
100 lost more than 40 pounds, and only about 1 in 10
even lost 20 pounds, with the overall successful weight
maintenance at only 2% over two years. That’s why having a control
group is so important. What may look like a general failure may
actually be a relative success compared to more traditional
weight loss techniques. Researchers new to the field may
find it clearly disappointing that a year later two-thirds were
“failures” with more than a third regaining all their weight
they had initially lost. But 12 percent were labeled successes, maintaining 59 pounds of
weight loss two years later. They lost massive amounts of
excess weight and kept it off. In a direct comparison of different weight
loss approaches at the same clinic, five years after initiating a
conventional low-calorie approach, only about one in five was down
20 pounds compared to nearly half in the group who instead had undergone
a few weeks of fasting years previously. By year seven, most of those instructed
on daily caloric restriction were back to, or had exceeded,
their original weight, but that was only true for about
one in ten of the fasted group. In an influential paper in the New England
Journal of Medicine on seven myths about obesity, fallacy #3 was that
“Large, rapid weight loss is associated with poorer long-term
weight-loss outcomes, as compared with slow,
gradual weight loss.” In reality, the opposite is true. The hare may end up
skinnier than the turtle. Researchers set up a study comparing
the sustainability of weight loss at three different speeds:
six days of fasting, versus three weeks of a
very-low-calorie diet, 600 calories a day, or six weeks of a
low-calorie diet, 1200 calories a day. The question is what
happened a year later? A year later, the fasting
group was the only one that sustained a significant
loss of weight. That was just one year, though;
how about nine years later? This is the largest, longest
follow-up study I could find. At least some of the
fast-induced weight losses were maintained a year later
by the great majority. A year later, 90 percent remained
lighter than they started out, but then two years later,
three years, four years, seven years, and by nine years later that number
dropped to fewer than 1 in 10. By then almost everyone had regained
the weight they initially fasted away. Many patients reported they thought that
temporary loss was worth it though. As a group, they lost an
average of about 60 pounds. They described improved health and
quality of life, claiming re-employment was facilitated, and earnings increased
during that period of time. But the fasting didn’t appear to
result in any permanent change in eating habits for
the vast majority. The small minority for which fasting
led to sustainable weight loss “all admit to a radical change
in previous eating habits.” Fasting only works long-term if it can
act as a jumpstart to a healthier diet. In a retrospective long-term
comparison of weight reduction after an inpatient stay at
a naturopathic center, those who were fasted lost
more weight at the time, but at around seven years
were back to the same weight. No surprise since they reported returning
to the same diet they were on before. Those who were instead
placed on a healthier, more whole food plant-based diet were more likely to make persistent changes
in their diet and seven years later were lighter than when they started. Why can’t you have it both ways, though? You could use fasting to kickstart a big
drop and then start a healthier diet. The problem is that big
drop is largely illusory. Fasting for a week or two can cause more
weight loss than calorie restriction, but paradoxically, it may actually
lead to less loss of body fat. Wait, how can eating fewer
calories lead to less fat loss? Because during fasting your body
starts cannibalizing itself and burning more of
your protein for fuel. Emperor penguins, elephant
seals, and hibernating bears can survive just burning fat without
dipping into their muscles, but our voracious big brains appear to
need at least a trickle of blood sugar, and if we’re not eating any carbohydrates
our body is forced to start turning our protein into sugar to burn. Even just a few grams of carbs, like
people who add honey to their water when they fast, can cut protein
loss up to 50 percent. What about adding exercise to prevent
loss of lean tissues during a fast? It may make it worse! At rest most of your heart
and muscle energy needs can be met with fat, but
if you start exercising they start grabbing some of the blood
sugar meant for your brain, and your body may have to
break down even more protein. Less than half of the weight loss
during the first few weeks of fasting ends up coming from your fat stores. So, even if you double your
daily weight loss on a fast, you may actually be
losing less body fat. An NIH-funded study placed obese
individuals on an 800-calorie-a-day diet for two weeks and they steadily lost
about a pound of body fat a day. Then they switched them to about
two weeks of zero calories, and they started losing more
protein and water but, on average, only lost a few ounces of fat a day. When they were subsequently
switched back to the initial 800-calories-a-day for a week, they
rapidly replaced the protein and water; and so, the scale registered
their weight going up, but their body fat loss accelerated back
to the approximate pound a day. The scale made it look as
though they were doing better when they were completely fasting, but
the reality is that they were doing worse. So, during the five-week experiment
they would have lost even more body fat sticking to their calorie-restricted diet than completely stopping
eating in the middle. They would have lost more body
fat, eating more calories. Fasting for a week or two can
interfere with the loss of body fat, rather than accelerate it.

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