Category: Science

As we saw in the last post, a valuable lesson can be learnt from the Biggest Losers: weight loss is not a matter of willpower, and certainly not a simple matter of eating less than you burn. In order to lose weight, you need to modify your metabolism. This is not easy, but it’s not impossible either.

It’s true that our body fat is regulated by several factors over which we have little control, such as genetics or past behavior, but there are steps that can be taken towards a healthier metabolism.

Note that being thin is not necessarily healthy, and that body fat is not necessarily a problem. It is the underlying causes of body fat that pose a health threat, as well as bringing the undesired fat.

Actually, all these causes are related to one and only one item: excessive blood sugar. We will explore a few of the mechanisms below, but there are many more.

1. Elevated insulin, a consequence of high blood sugar, puts the body in fat storage mode.

During digestion, carbohydrates are broken into simple sugars and passed into our bloodstream. The elevation in blood sugar causes the pancreas to produce insulin, a hormone that allows the cells to let sugar in.

The glucose (sugar) taken away from the blood and into the cells can be used to provide immediate energy. If energy is not needed, sugar is stored as glycogen. When the glycogen storage is full, the remaining glucose is stored as fat in fat cells.

Insulin activates the enzymes that enable fat storage and impairs the action of hormones that release fat from fat cells: high insulin signals that glucose (i.e. immediate energy) is available; fat is therefore not needed and should be stored for later use.

2. Elevated blood glucose induces the enzymes that favor using sugar for energy (and impairs the enzymes that are necessary for burning fat).

The bulk of our energy is generated through cellular respiration, a complex series of chemical reactions that take place in the mitochondria in our cells.

The body is a marvelously adaptable machine that can work with whatever it has. If there is a lot of glucose in the blood, the body will produce the enzymes to burn glucose for energy. If the body sees less glucose, it will generate the enzymes that burn the fat instead.

3. Elevated blood glucose next to fat cells locks the fat inside the cells.

Fat is travelling in the blood or stored in cells under the form of triglycerides.

The molecules in the fat tissue are in constant motion, crossing the cell walls into the blood stream and back. Since triglycerides cannot cross the cell walls, to go in and out of the cell, they are disassembled into free fatty acids and glycerol and reassembled into triglycerides on the other side of the wall.

This process is also regulated by the levels of insulin and blood sugar: insulin causes fat cells to take in glucose and burn it for fuel; this produces a glycerol-phosphate molecule, which in turn provides the glycerol molecule that binds with free fatty acids to create triglycerides.

Thus, burning glucose in the fat cells reduces the number of free fatty acids that can escape the cell and increases the proportion of fat locked as triglycerides inside the cell.

There are several more mechanisms that cause fat to be stored, all involving sugar. Very surprisingly, these facts have eluded most weight loss researchers for a century. Instead, the notion that eating fat makes you fat still prevails.

(To be continued…)

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A KQED broadcast last week (May 2, 2016 – All Things Considered) reported on a study that examined what happened to the participants in the TV reality show The Biggest Loser after the show was over. A (not too surprising) fact was that many of them regained much of the weight they had lost during the show.

One of the report’s conclusions was that body weight is biologically determined and that “it’s not just a matter of willpower to produce weight loss and to keep weight off.” It seems that the body wants to regulate its fat content to a set point, like a spring: you can compress it, but as you let go, it returns to its original position.

No surprise

This finding, of course, doesn’t come as a surprise. Anybody that has been on a weight loss diet could have told you that. With the risk of sounding conceited, this result was highly predictable, not to say inevitable.

So why do most people still believe that after going on a weight-loss diet, they can return to their old ways and still keep the weight off?

This has always seemed odd to me, until I examined the prevailing weight-loss beliefs more in depth.

It turns out that most people, including doctors and health professionals, view the body as a calorie bag: if you eat more calories that you expend, you gain weight; if you spend more than you eat, you lose weight. Before people embark on their lean quest, their weight is more or less constant (maybe several pounds higher than they wished, but stably so). The logical deduction is that what they are eating balances exactly what they expend. Therefore, if they could only lose the extra pounds, they’d be fine and could resume their old lifestyle happily ever after. QED.

Logical? Well the fact that this scheme doesn’t work should be proof enough that the “calorie in – calorie out” view of weight control is incorrect.

Regulation – The Spring effect

Actually, how fat is stored in our cells is a complex, regulated system, the body trying hard to stabilize the amount of fat around a set value.

This set value is a function of our genetics, as well as our long term nutritional behavior, environment and medical history; with age our body is less resilient, and coping with excesses becomes more difficult.

Still, another sensible line of reasoning says that you can’t produce something out of nothing, and that, in order to gain weight, you have to take in more calories than you consume. After all, like gravity, thermodynamics are not just a good idea, they are the law! So how can a weight-loss contestant eat less than ever, keep-up the exercise, and still gain the weight back? Read on…

Somewhat of a surprise (but not that
much)

One contestant interviewed explained that she had worked extremely hard at shedding the original weight: it took a grueling regimen of diet and exercise. Listening to her, one could sense that she is a very strong-willed person; nobody could suspect her of being lazy or self-indulging. Yet after she gained the weight back, she found it nearly impossible to lose it again.

The interesting “discovery” of the study was that after they lost weight, the people’s basal metabolic rate (BMR, amount of energy expended while at rest) was disproportionately low compared to the rest of the population: these people needed to burn less calories to sustain their weight than people with the same weight that have never been on a weight reduction program. Conversely, these weight-reduced people needed to eat less than the other people in order to sustain their weight.

Another interesting observation was that, after they regained their weight, the people’s BMR was still low. That contributed to make losing weight the second time around even harder.

There is a prevalent view that muscles burn more calories than fat, and that if you lose fat and build-up muscle, your metabolic rate will increase. The study’s findings go against that theory.

A conclusion

The “calorie in – calorie out” view of the body has been proven wrong over and over again. To reach your ideal weight, you need to improve your metabolism. This goes way beyond “eating less and exercising more”. It includes changing your metabolism, lifestyle and especially your nutrition.

Calorie restriction makes you metabolically weaker.

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