There are many reasons for weight loss to slow or stop while low-carbing. Read any of Dr. Atkins’ books or follow any of the low-carb websites and you will find lots of possible explanations, including factors like low thyroid function and yeast infections.

Another reason for failure to lose weight and for weight regain on low-carb is seldom mentioned. An example is pictured above–low-carb substitutes for high-carb foods. (The picture is taken from a post about a low-carb sponge cake at Cafe Nilson.) But low-carb substitute foods are still low-carb! Why should they interfere with a low-carb diet?

A 2005 study on binge eating in rats may give some insight. In one experiment, the rats were separated into two groups, food-sated and food-restricted. They were then exposed to several food choices, including normal rat chow and a cereal called “Choc and Crisp” which appears to be a German version of Cocoa Krispies. The food-restricted rats took about three minutes to find the rat chow, and they ate about half a gram of it. By contrast, they found Choc and Crisp in only ten seconds and when they reached it, they ate nearly five grams of it.

As expected, the food-sated rats were not interested in the rat chow. They took about 20 minutes to wander over to it and when they got there, they didn’t eat it. However, even though these rats had already eaten until they were full, the food-sated group took one fiftieth of that time (25 seconds) to find the Choc and Crisp, and once they reached it, they ate 3 grams of it, or 60% of the amount the food-restricted rats had consumed.

To confirm these responses, each rat was put on a runway with a food-filled box at the other end. When the goal box contained rat chow, it took the food-sated group about 40 seconds to reach the goal, while the food-deprived ones took about 10 seconds. Not surprising. However, when the goal box contained Choc and Crisp, both groups made the trip in about five seconds, though the food-restricted group was a little faster. One might expect that after the first day, the rats would be less excited about the Choc and Crisp, but the time needed to reach the goal boxes persisted over ten consecutive trial days.

The obvious conclusion is that if you feed pet rats with Cocoa Krispies, they will probably get fat. A less obvious inference might be that if a low-carber is freqently exposed to low-carb versions of very enticing high-carb foods, he or she will probably eat those foods to excess. The rat study indicates that the easy availability of very palatable foods may shut off the body’s ability to adjust food intake to match energy expenditure. What happens in a rat does not necessarily happen in a human, but their tendency to eat much more of a very palatable food is definitely something to consider when low-carbers have a hard time reaching or maintaining their goal weight.

Doctor Annika Dahlqvist was a family practitioner at the Njurunda clinic in Sweden when her daughter, a physician in training, took part in a low-carbohydrate dietary study. The results were so impressive that Dr. Dahlqvist tried the low-carb diet for herself. She was pleased that she was able to lose weight, and she also noticed that her problems with gastrointestinal inflammation and fibromyalgia were significantly improved. She began recommending a low-carb, high-fat (LCHF) diet to her patients who suffered from type 2 diabetes and obesity.

The idea of a low-carb, high-fat way of eating was no more welcome in Sweden than it has been in the United States. In December 2005, the chairman of the Swedish National Association of Dieticians made a formal complaint to the Swedish National Board of Health and Welfare, questioning Dr. Dahlqvist’s low-carb dietary advice and suggesting that it might jeopardize the safety of her patients. Dr. Dahlqvist was threatened with the loss of her medical license.

Although Dr. Dahlqvist’s LCHF diet was quite compatible with a traditional Atkins-type diet, she stopped treating patients and instead began working on a blog and giving lectures to spread the word about LCHF.

Flash forward to January 17, 2008.

Professor Christian Berne, one of Sweden’s leading diabetes experts, had carefully investigated the case against Dr. Dahlqvist and presented his findings to the Swedish National Board of Health and Welfare. He said, “…a low-carbohydrate diet can today be said to be in accordance with science and well-tried experience for reducing [obesity] and type 2 diabetes…a number of trials has shown no effects in the shorter run and that no evidence for it being harmful has emerged in systematic literature researches performed so far. [There is] no scientific support yet for treatments in excess of 1 year. A thorough evaluation of long time treatment results is therefore an important demand on the practitioner.”

By objecting to the low-carb, high-fat diet, the chairman of the Swedish National Association of Dieticians had inadvertently given it validation. In fact, because of the governmental investigation into the scientific support for LCHF, the diet was approved as an alternative approach for the treatment of type 2 diabetes and obesity. New Board guidelines are expected to be completed by autumn of 2009.

As for Dr. Dahlqvist, she continues to lecture, to blog, and to gain in popularity in her native land. In 2008, Radio Västernorrland listeners chose her as Personality of the Year. The seventy percent who voted for her said, “…she stood up against the Health and Welfare and Food Administration’s current dietary recommendations, campaigning instead for a diet she believes in—low in carbohydrate but high in natural animal fat.”

Even more impressively, Swedish consumers have started to consider whole milk and butter more natural and healthful than reduced-fat products and are now changing their habits to buy more of the former and less of the latter. There are still plenty of dietary traditionalists in Sweden, but for some people at least, butter is now a health food.

One of the important aspects of fat is that it is not water-soluble. In order to begin the digestion process, the liver makes bile, which in collected in the gallbladder and is secreted into the small intestine. The bile acts as a detergent. The bile salts in it have a lipophilic side, which binds to the fat droplets, and a hydrophilic side, which suspends the droplets in the watery mixture of the food we have just eaten.

The triglycerides or fats in the suspended droplets cannot be absorbed by the intestine. To accomplish absorption. the pancreas secretes an enzyme called pancreatic lipase into the small intestine, Pancreatic lipase breaks down each triglyceride molecule into two free fatty acids plus a monoglyceride. “Mono” means one, and in this case it means that one of the fatty acids remains attached to the original glycerol backbone. When the triglyceride is broken down into subunits, it is able to pass into the absorptive cells of the intestinal mucosa. After the three subunits have transited the wall of the intestine, the fatty acids are added back to the glycerol backbone and they form a triglyceride once more.

Inside the cells of the intestine, triglycerides are packaged into chylomicrons. Chylomicrons are large diameter (75-1200 nanometer) particles that contain a bit of protein, a bit of cholesterol and lots of triglycerides. The chylomicrons are not secreted directly into the blood but into the lymphatic system. They eventually arrive at the thoracic duct and then are deposited into the blood at the left subclavian vein. Once they enter the blood, they are transported into capillaries and are able to reach the entire body.

One of the proteins in a chylomicron is called apo C-II. This protein has the ability to activate an enzyme called lipoprotein lipase or LPL. Lipoprotein lipase resides on the capillary walls of tissues that have a high requirement for triglycerides, such as cardiac muscle cells, skeletal muscle cells and fat (adipose) cells. The activated lipoprotein lipase acts on the triglyceride molecules (called triacylglycerols in the illustration above) stored inside the chylomicron. It hydrolyzes or breaks down the triglycerides into two fatty acids plus a monoglyceride. Just as we saw in the intestine, intact triglycerides cannot pass through the cell walls, but when they are hydrolyzed into subunits, they can be absorbed into the cells. Once inside, they can be used for energy in the muscle cells or reassembled into triglycerides and stored in the adipose cells.

When we eat a piece of bacon, we start with fat and end with fat (or for the low-carber–energy from the fat). But, as you can see, there are may steps involved in getting from the beginning of the process to the end.

In a word–yes. Proteins are linear molecules made of building blocks called amino acids. Proteins are synthesized within cells by an organelle called a ribosome that reads the “recipe” for each particular protein from another linear molecule called RNA. As the ribosome reads the RNA, it looks in its immediate vicinity for whichever of the twenty different amino acids is called for next in the sequence. If the ribosome comes to a point in the RNA “recipe” where the corresponding amino acid cannot be found, the ribosome falls off the RNA and synthesis of the protein stops. Until there is enough of the missing amino acid, that specific protein cannot be made.

Where does the missing amino acid come from? Some amino acids like alanine, glutamate and asparagine, can be made by our bodies. Unless there is an inborn error of metabolism, these amino acids are present in abundance. However, other amino acids like lysine, methionine and tryptophan cannot be made by the human body. These are called essential amino acids and they must be consumed as part of the diet. If any essential amino acid is not consumed in sufficient quantity, its absence shuts down much of the body’s protein-synthesis machinery.

Cereal grains such as corn, millet, rice and wheat are typically low in the amino acid lysine. Even though a person consumes many grams of protein in the form of cereal grains, the low abundance of lysine will prevent his or her body from making many of the proteins it needs for growth and repair. Legumes such as beans and peanuts are low in the amino acid methionine. Eating lots of beans or peanuts will provide lots of protein, but when the plant protein is broken down into its amino acids and these are then used for human protein synthesis by ribosomes, the ribosomes will be unable to find enough methionine to produce the proteins the body needs to sustain itself. When a food source is deficient in one or more essential amino acids, it is said to contain incomplete protein. Incomplete protein can be used as a source of calories or energy, but it is inefficent in meeting the body’s need for human protein synthesis.

It is possible to mix plant sources of protein such as corn and beans in order to obtain a better overall amino acid profile. However, the complementary sources must be consumed within several hours of each other or the beneficial effect will be lost. The complementarity must also be well-understood. For instance, almonds are low in lysine and methionine, so addition of cereal grains or legumes to almond protein will still result in poor protein nutrition. Another aspect to consider is the fact that plant sources of protein are often more difficult to digest than proteins found in animal sources such as whey, meat or eggs. If the plant products are refined, digestibility is improved, but nutritional quality is lost.

Animal sources of proteins typically have a much better balance of essential amino acids than plants do. When you think about it, that makes sense. Plants do not use their proteins to make blood, muscles or organs. Plant proteins are used for different funtions, and the amino acid profiles of those proteins are unique. On the other hand, animals are similar to people in many ways, and their proteins require about the same percentage of amino acids that are required to make proteins having similar functions in humans. Good sources of animal protein include whey protein, casein (cheese), eggs, meat and fish. An interesting comparison of protein quality can be found here. As the chart in that link indicates, plant protein from soy does provide a complete array of amino acids. However, because consumption of soy products may be associated with alterations in hormone levels, they should be used with caution.

Protein is an important macronutrient. It has many beneficial primary and secondary effects, but if the protein consumed is not of high quality, i.e., if it is not complete protein, the body will not be able to use it effectively to make and repair skin, nails, hair, bone and muscle.

Layman begins by discussing the fact that protein has traditionally been thought of as an expensive nutrient. While that’s true in the context of managing animals in a feedlot, it is a little less true in a human society where families are willing to pay $5.00 for a box of breakfast cereal. Nevertheless, because we have been conditioned to think in terms of eating small amounts of protein, it is important to establish how much protein is enough.

The Institute of Medicine, Food and Nutrition Board, has established a recommended daily allowance (RDA) between 0.36 grams and 1.1 grams of protein per pound of total body weight. The important aspect of the protein RDA is that it is proportional to current body weight. It is not a percentage of daily caloric intake. In other words, a man who weighs 200 pounds needs to eat a minimum of 72 grams of protein daily. It doesn’t matter if his typical caloric intake is 3000 calories per day or if he is dieting and eats only 1000 calories per day. Regardless of his total caloric intake, he should be careful to consume at least 72 grams of protein every day.

Layman points out that the Nutrition Board has not identified an upper risk limit for the amount of protein a person can consume in a day. In other words, a normally healthy person should be able to eat as much protein as he or she wants to. With that in mind, let’s take a look at some of Layman’s observations in this article.

1. Protein provides a greater satiety value than fats or carbohydrates and reduces food intake at subsequent meals. This effect is seen when protein intake is over 30 grams at a meal, is strongest when the protein is consumed at breakfast and is weakest when it is consumed in the evening.

2. Compared with high-carbohydrate/low-fat/low-protein diets, weight loss diets with higher protein increase thermogenesis and increase the rate of fat loss. When combined with exercise, weight loss diets that are rich in protein can reduce lean tissue loss from 35% to less than 15% and protect from bone loss as well.

3. In children and young adults, skeletal muscle synthesis is regulated by insulin secretion and caloric intake. However, in older adults, this switches to a pathway regulated by the essential amino acid leucine. To protect themselves from age-related loss of lean muscle, it is important for older adults to eat more than 30 grams of protein at least two or three times a day.

4. Exercise, calcium supplements and vitamin D are important for the prevention of osteoporosis. However, in the elderly, it has been found that calcium supplements will not be effective against osteoporosis unless the daily protein intake is greater than 0.55 grams per pound of total body weight.

5. In type 2 diabetics, replacement of dietary carbohydrates with protein has been observed to decrease hyperglycemia, reduce post-prandial hyperinsulinemia, and improve HbA1c.

As the wise man said…getting old is definitely better than the alternative. But perhaps these recent studies have shown us that the symptoms of aging can be slowed down a bit in people who are willing to eat more protein.

In 1989, L.H. Schneider observed that dopamine receptors in the brain are stimulated when rats are allowed to feed themselves sweet solutions. Since that time, many investigators have noticed a relationship between either the taste of sweet or the actual consumption of sweet and the response of dopamine receptors in the brain, both in rats and in humans.

Dopamine is a neurotransmitter found in the midbrain. It has many functions, but one of them is the ability to produce prolonged feelings of pleasure. Increased dopamine signaling is involved in the mechanism of addiction to cocaine, amphetamines, and nicotine. At a more moderate level, novel foods, sweet foods, and overeating also cause increases in brain dopamine.

In order to investigate possible rebound effects of overstimulation with dopamine followed by abrupt dopamine withdrawal, a group of rats was treated for five days with l-dopa (a substance which is converted to dopamine in the brain). The research is described in an article in the December 2008 issue of Nutrition & Metabolism. After treatment was completed, the rats in the previously-treated l-dopa group were compared with an untreated control group. Over the next 12 weeks both groups of rats were allowed to eat as much food as they desired. At the end of that time, the previously-treated rats had gained 15% more weight than the control group.

Why did this happen? The authors hypothesize that treatment with the dopamine precursor l-dopa caused overstimulation of the dopamine signaling system in the rats. This, in turn, caused downregulation of dopamine receptors and decreased endogenous dopamine production. When the l-dopa treatment ceased, the rats were left with few dopamine receptors and low endogenous dopamine production. To compensate for this, the rats used the mechanism of overeating to compensate for their relative dopaminergic deficiency.

Rats are not humans. Nevertheless, it is possible to suggest that eating or tasting sweet food causes an overstimulation of the dopamine signaling system. This produces a downregulation of dopamine signaling such that, in the absence of sweet, there is a noticeable decrease in energy, motivation and mood. Sweets are legal, cheap and easy to obtain. If the sweet-eater wishes to experience the pleasant feelings associated with dopamine overstimulation, it will be very easy to continue eating sweets. And if he is unable to wait several days to a week to allow the body to return to its normal level of dopamine production and receptor activity, it will be harder than he might have expected to eliminate sweet tastes from his diet.

The article, called Modified sham feeding of sweet solutions in women with and without bulimia nervosa, was designed to show whether people who experience binge-eating episodes might overrespond to the stimulations of taste and smell. As it turns out, they do not, or at least they did not in this study. However, the study did produce an interesting outcome in terms of the way people respond to sweet tastes.

The study compared two groups of women–ten healthy women (termed NC, or Normal Control) and eleven women with Bulimia Nervosa (termed BN). The women were given solutions of cherry-flavored Kool-Aid sweetened with aspartame in concentrations of 0, 0.01, 0.03, 0.08 and 0.28%. (The 0.08% solution approximates the sweetness of commercial soda.) There were three trials in which the five solutions were prepared in five opaque containers, each fitted with a straw. The solutions were presented in a random order, using a one-minute access period during which the women could sip as much as they wanted of that particular solution, but they could not swallow it. They were instructed to spit out the solution into another opaque container. (The amount sipped and the amount spit out was later measured by the investigators.) The women were then asked to

1. Rate the sweetness of the solution

2. Rate how well they liked the solution

3. Rate how much they wanted more of the solution

Even though the solutions were presented in random order, both the Normal Control group and the Bulimia Nervosa group were able to accurately distinguish among the five levels of sweetness provided in the solutions. Again, although the solutions were presented randomly, both the Normal Control group and the Bulimia Nervosa group reported liking the solutions in direct proportion to how sweet the solutions were. Consistent with the self-reported preference rating, both groups sipped an increasing amount of the solution as the sweetness of the solution increased. (Remember, they were not allowed to swallow the solution, but they could sip as much of it as they wanted.) Finally, as shown in the graph below, both groups reported that they wanted more of the solution as the sweetness of the solution increased.

For both groups of women, more sweetness led to more liking, more sipping and more wanting. This was not a function of actually consuming the sweetened solutions, but simply of having the solutions in their mouths for a few seconds. Using this information, it not unreasonable to suggest that the increased use of another sweet substance, high fructose corn syrup, in all sorts of foods, may have the unintended result of producing more liking, more eating and more wanting of the products that contain it.