On an individual level, when it comes to calorie intake, fat mass and energy expenditure some people appear to be “spenders” and some “savers.”
Are you a spender or a saver? Responsible mother and father teach their offspring to save at least part of what they earn to build a nest egg, or purchase something special later— if you get a bonus or unexpected windfall, don’t spend it all, save some.
There was a story of the ant and the grasshopper where the grasshopper would have died over a harsh winter, because he ate everything as soon as he saw it. His grace came from the generosity of the ant that worked and saved, storing food for hard times.
These are important lessons, told by survivors who made it through times of famine or depression. The human body learned these lessons while sitting on stones, feeling amazed at the power of fire. If you get energy (calories), save some (store it as fat) for a certain time of famine some time in the future. If you are in a famine, stop burning as many calories as you do in favorable periods. When it’s time of the harvest or a hunt is successful, gorge on the food, but don’t get wasteful with the calories by upping the metabolism any higher than necessary. Of course, just like with money, some bodies pay a lot of attention to this lesson while others are living on “metabolic credit” and burning calories like fireworks in the eyes of those that can’t lose excess fat.
On an individual level, some people seem to be “spenders” and others “savers” in terms of calorie intake, fat mass and energy expenditure. Everyone probably knows someone who eats miserly amounts, counting each calorie like a pauper counts pennies, and yet, the pounds just keep going up, and no diet ever seems to work more than for a few weeks. Then there’s the grasshopper who can eat his/her fill and more, but remain lean.
For the metabolic “savers,” things just seem to worsen after a diet. It seems as though the body’s metabolism has gone from burning calories to just having them smolder. This may account for some of the “yo-yo” dieting experienced by many individuals.
Is it a myth that some fail at diets or regain weight due to a metabolic shift to “saving?” Or is there a physiologic explanation, with evidence at the genetic and molecular level?
Researchers have discussed the existence of the “thrifty phenotype” for decades. Of course, dieters have long been aware of the fact that some people have a metabolism that turns sluggish the moment they order a salad instead of a cheeseburger. It’s like the mitochondria and fat cells have become wired for sound and can hear the words “Splenda” or “dressing on the side and order a work halt.
However, the term “thrifty phenotype” signifies more than feeling that the metabolism is sluggish; it’s something that can be measured and confirmed. Every person’s metabolism slows down when calories are dropped considerably, say by 30-45% of maintenance calories. In other words, if you usually need 2,200 calories a day only to maintain your weight, then dropping your daily calorie consumption to 1,210 calories a day will make your body adjust down its resting energy expenditure (roughly equivalent to the basal metabolic rate).
A number of trainers and dieticians use a standard formula to calculate maintenance calories, which fits about as good as any “one-size-fits-all” item (it works for everybody kind of, and no one well). Of the more than 200 formulas, the Harris-Benedict equation is probably the best known, though not necessarily best for many populations.
Nevertheless, there seems to be a divide, in that some people only adjust their metabolism down a little when dieting, while others do so to a much higher degree. The difference can be about 20% of the 24-hour energy expenditure (how many calories are burned throughout the entire day) according to rodent studies, but almost 50% when adjusted for weight.
To say it differently, when the calories were reduced to just more than half of the original maintenance calories, overweight “thrifty” rats burned only as many calories as “normal” rats that weighed half as much, on the same relative calorie restriction. These results were supported by a study in humans that showed a greater reduction in free T3 and free T4 (thyroid hormones) and higher level insulin; resting energy expenditure (metabolism) tended to stay “slowed” in those who gained weight back, though the result wasn’t statistically significant.
Adding insult to injury, when “thrifty” dieters stop their weight-reduction plan and return to normal eating, even adjusted for their new (hopefully lower) bodyweight, their metabolism doesn’t rev back up. Instead, they discover that their “maintenance calorie demand” is much lower than the “spenders” who turn up the heat (literally and figuratively) as soon as they begin re-feeding.
So, “thrifty” dieters might already be heavier, and more prone to fail in dieting using standard calculations, as they have a lower starting “maintenance” calories, and as soon as they start to reduce their calories, the physique seems to self-sabotage and pull back the throttle on the metabolism. This makes weight loss slower and harder. In addition, as soon as “thrifty” dieters start eating normally again, they gain weight rapidly because their metabolism doesn’t respond to the return of calories to burn. Instead, any extra calories over their comparably lower metabolic demand is more easily stored as fat.
LOW BIRTH WEIGHT AND POOR NUTRITION
Before taking a closer look at the findings of a controlled study in humans, consider the current understanding of the “thrifty phenotype” hypothesis. From its inception, this theory was inspired by the discovery that babies with low birth weight from mothers with poor nutrition were “skinny fat” because they had as much fat as normal-weight babies, but less lean mass. Additionally, these babies were born insulin resistant, with high leptin and insulin, as well as low adiponectin. This hormone combination presentation is the same seen in overweight prediabetic adults.
During fetal development (before the child is born), the fetus is reacting to the environment as it senses it through the mother’s circulation. If the mother has poor nutrition, then the fetus enters a survival mode, and the metabolism of that developing individual is programmed to preserve calories and energy. This is done to make sure that vital organs, especially the brain, receive enough nutrition first and foremost.
This programming is inserted into the lifetime response for the fetus, and persists into adulthood— maybe even being passed on to later generations. It’s an example of epigenetics.
Of course, psychologist Sigmund Freud would have had a celebration, given that this is something that may be blamed on a person’s mother. Of course, women living in impoverished areas have no choice in the matter, trying their best in most cases to provide for their baby. Nevertheless, even in prosperous countries, such as the United States, poor nutrition remains to be rampant among the socio-economically challenged. There may be food and a lot of calories, but the nutritional value of the usual diet for many is lacking in many essential micronutrients—especially a pregnant woman/teen.
IMPACT ON WEIGHT LOSS
A paper recently published in the journal Diabetes followed a group of people, after determining with considerable precision and effort not only their basal metabolic rate, maintenance calories, sleeping energy expenditure, response to one-day caloric restriction (50% of maintenance calories) and one-day overeating (200% of maintenance calories).
Activity was also measured using five sensors positioned on the limbs and trunk. This initial set of determinations occurred in a closely controlled environment, where not only were activity and food controlled, but also the ambient temperature. For almost two weeks, the group adjusted to this setting. They were overweight, but otherwise healthy, and not allowed to exercise for the duration of this study (eleven weeks total).
The baseline measurements were determined twice for accuracy, the second occurring after the maintenance calories were shown to maintain weight within 1% of the weight at the beginning. Very demanding and rigorous study for the subjects and researchers. Then, the subjects spent one month and a half in the same controlled environment, but were placed on a diet providing only 50% of maintenance calories. As might be expected, all the subjects dropped pounds, however, there was a very clear divide. During the initial phase, certain subjects were discovered to quickly and dramatically lower their 24-hour energy expenditure (total number of calories burned during the day), and they didn’t “turn up” their metabolism or activity as much when overfed. Others were discovered to only drop the 24-hour energy expenditure a bit, and when they were overfed, their metabolism revved up on a supercharger.
When the data was analyzed comparing those who were “thriftiest”— in other words, they slowed down their metabolism most when calorie restricted and didn’t waste calories by burning them when overfed— there was a clear difference. While all groups lost weight— after all, they were consuming only half as many calories as they needed — the “thrifty” didn’t lose as much weight.
Then, the subjects were placed back on a maintenance calorie food plan for another two weeks, and re-tested to find out how they responded to calorie restriction or overeating after losing weight. Again, it was discovered that the “thrifty” showed a disadvantage in regards to weight loss. Their maintenance calories were lower than what the calculated value would be based upon weight, fat mass and fat-free mass.
An interesting observation is that both groups, “savers” and “spenders,” had pretty much the same sleeping energy expenditure, which means that the basal metabolism wasn’t necessarily revved up in the “spenders.” Instead, the 24-hour energy expenditure was increased. While those dropping the most pounds were also the least sedentary, that difference didn’t account for the majority of the weight lost.
Beside potential hormonal changes previously noted in earlier studies (thyroid hormone, insulin, leptin, etc), the authors speculated that diet-induced thermogenesis could account for some of the difference. Brown fat is a heat-producing tissue that’s activated by the sympathetic nervous system, cold conditions and food intake. The building was temperature-controlled, and the participants were sedentary and not allowed access to thermogenic drugs or supplements.
So, the researchers feel it may be possible that the “spenders” have more brown fat and burn calories with meals that the “savers” would save. Sadly, they didn’t measure brown fat, so that’s guesswork— but reasonable.
THINK ABOUT THE FOLLOWING
Two findings were most interesting: those who are less likely to benefit from dieting-based weight loss can be identified earlier than the diet starts, and the weight lost in sedentary people who only reduce calories to shed pounds is about 50:50 fat and muscle.
At least, this is true for an extreme caloric restriction diet. If you’re a spender, you in all probability are pretty successful dropping weight when you need to, and when you overeat, feel your body heating up. If you are a saver, it’s not a pre-destined failure. Instead, it could be advance notice that more aggressive tactics are needed than just reducing calories. Hopefully, people aren’t reducing calories down to 50% of maintenance (50% carbohydrate, 30% fat, 20% protein was used in the study).
Furthermore, this shows the need for higher protein intake and more resistance training when trying to lose fat weight. Perhaps, the research brown fat activation, even transplantation, might level the playing field one day between “spenders” and “savers.”