The link between brain and belly

Individual levels of certain neurotransmitters can help determine what kind of diet will work best.

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April 11, 2010 09:35
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The aphorism that “You are what you eat” recognizes the important effects of diet on health. But recent studies seem to show that the mirror image – “You eat what you are” – is true as well.

This means that the level of certain neurotransmitters – especially serotonin and norepinephrine – in the brain not only affect moods but also determine what type of diet would be most effective in helping you lose weight – and keep it off.

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Prof. Ilana Blum, a Hebrew University Medical Faculty graduate who specialized in internal medicine and endocrinology, has just published a  Hebrew-language book on this subject. Called Lirzot Behochma! Al Ochel, Matzav Ruah, Mishkal Vechol Ma Shebeineihem (Losing Weight Wisely! Food, Mood, Weight and Everything in Between), the 199-page volume will be an eye opener to the many people who have lost weight and gained it – and more – back.

Published by Yedioth Books (www.ybook.co.il), the NIS 118 softcover offers much to the layman, but is also full of scientific explanations for Blum’s advice. The author, who was assisted in the writing by Rina Lipa, was previously director of an internal medicine department at Tel Aviv Sourasky Medical Center and ran the endocrine institute at the Rabin Medical Center-Beilinson Campus. She is also the author of many studies on hormonal changes and brain function, and the influence of nutrition on how the brain works.

WITH A cover focusing on a bunch of lovely thin, lime-colored asparagus, the book does not preach consuming only low-calorie vegetables. It suggests that those who want to lose weight permanently adopt a healthful lifestyle and diet suited specially to them. They should go for a blood test to check serotonin levels, which unfortunately is not paid for by one’s health fund unless a physician deems it necessary. If not, the test can be done privately for about NIS 150.

When serotonin is high, norepineprine is low and vice versa; thus it is usually enough to check only the former.

The results determine whether a high-carbohydrate or high-protein diet or combinations of those and other nutrients will help you reach your ideal weight. Once you reach that target, maintains Blum, your body is likely to “protest” if you change the diet, and even make you feel uncomfortable.



The 30 chapters, sharply illustrated in black, green and grey tones and with different foods hugged in their midsection by a measuring tape, are written with many details. Nevertheless, the text does not talk down to the laymen reader. The chapters include a glossary and index, as well as 24 pages of weekly menus according to one’s neurotransmitter level type, and 10 pages of recipes. These are very varied, interesting and easy to make and clearly do not aim to make readers subsist on dull, repetitive fare. The author says that the easier a recipe is to make, the more likely one is to stick to it.

Blum begins that many people who want to lose weight find they are caught in a yo-yo diet, losing and then gaining weight, only to seek to lose those excess kilos again. Individuals who have a tendency toward depression have an even more difficult time losing weight for various reasons, and this is a major clue to breaking one’s diet. “It is well known that food is often self-compensation for a lack of love, for anger and emotional tension,” she writes.

Her book offers “not just another diet but constitutes recommendations for a balanced lifestyle that makes it possible to lose weight and preserve the new weight while improving mood without starving oneself,” she writes. Blum was surprised and even thrilled when some of the hundreds of healthy volunteers she tested – some with a follow up of as long of 15 years – developed stomach aches or diarrhea when they abandoned it and were thus persuaded to stick to it for a long period. Thus the diet is self enforcing. But it is flexible enough to allow occasional “sinning” by eating in a restaurant on special occasions or attending a social event.

WEIGHT CAN be lost even without physical activity, Blum notes, but regular exercise of course speeds up the weight loss and can improve moods even more, as well as improve health of the heart, lungs, blood vessels and other organs and tissues.

She recalls the case of a 40-year-old man who was hospitalized with an infected sore on his foot – a well-known complication of uncontrolled diabetes. Weighing 300 kilos and breaking the hospital scale, the extremely obese man was unable to lose weight, despite the hospital’s efforts – and died of heart problems two years later.

But the case of a 70-year-old obese woman who suffered from knee damage due to her girth had a happy ending. Her orthopedic surgeon told her he would refuse to operate to fix her damaged knee unless she reduced her weight. She was helped to lose 40 kilos, underwent successful orthopedic surgery – and the quality of her life was transformed.

Blum explains how being overweight causes harm to a large number of organs. Aside from heart attacks, strokes, kidney damage, joint disorders and fatty liver disease, overweight and obesity can reduce one’s fertility and lead to cancer. Everyone should by now know his personal Body Mass Index (weight in kilos divided by the square of meters in height). From 18.5 to 24.9, one has normal weight; below that is underweight, while above it is overweight; a BMI over 30 means obesity. Having excess abdominal fat is the most dangerous to health.

Overweight and obesity are caused by a combination of genetic and environmental factors, but Blum says one can overcome both of these. Children who had a low birth weight tend to become overweight as adults and to develop insulin resistance as adults. Blum explains that the infant body interprets the low body weight as “stress” and causes the endocrine system to release stress hormones such as catecholamine and cortisol; these increase insulin resistance, which can lead to diabetes unless caught in time. But a diet heavy with fats and calories and a lifestyle without exercise have the same effect.

SHE ALSO discusses substances – from progesterone to ghrelin – that promote appetite, and other substances that suppress it. Blum writes that for decades, it has been known that neurtransmitters such as monoamines are responsible for changes – often extreme – in moods. This class of neurtransmitters includes dopamine, norepinephrine, epinephrine and serotonin – and these affect appetite as well. A shortage can lead to depression and too much can cause ‘high’ moods and – in the extreme – mania and schizophrenia. Food also affects our moods, she adds.

Studies show that even one meal can temporarily change one’s mood and level of functioning. The different sexes react differently to the same meal. Women report sleepiness after a meal high in carbohydrates like pasta, rice, cake or potatoes, while men report relaxation and calmness following the same meal.

But not only gender affects the reaction to food; age and the time of the meal do as well. People over 40 who eat a high-protein diet tend to feel more tense. A high-carbohydrate lunch can cause reduced tiredness and lower concentration. A high-fat lunch can cause slower but more accurate responses to questions than a high-carb meal.

Serotonin rises after a high-carb meal by up to four times its basic level, and drop to one-quarter of its basic level after a high-protein meal. Norepinephrine levels were not affected by the carbohydrates, but rose significantly in reaction to a high-fat diet.

People who prefer carbs are born with a genetic makeup that causes a shortage of serotonin in the brain, so they try to compensate for this by eating a lot of carbs, Blum writes. Most overweight people suffer from insulin resistance; insulin causes tryptophan – the raw material used to produce serotonin – to pass the blood/brain barrier. This mechanism results in a shortage of tryptophan, causing the serotonin level to drop. This explains why 70% of overweight people suffer from light to moderate depression. Meanwhile, individuals who prefer proteins such as meat, eggs and dairy foods have relatively high levels of serotonin and low levels of norepinephrine.

Thus, declares Blum, a menu can be devised that raises serotonin levels without comprising a lot of calories; this can bring about both weight loss and improved mood.

Individuals with low serotonin levels should get 65% to 70% of their diet from complex carbs (such as brown rice and full-grain bread or pasta), 15% from fats and 15% from proteins to raise serotonin levels, Blum prescribes. Carbs and proteins should be eaten separately, at least three hours apart.

Those with normal serotonin levels should eat a diet of 50% to 55% complex carbohydrates, 30% fats and 20% proteins.

People with high levels of serotonin should eat a high-protein diet, with 40% to 50% protein, 30% to 40% complex carbohydrates and 20% fats.

People suffering from insulin resistance should eat a high-protein diet in the first stage because sugar does not succeed in entering their cells, causing blood glucose levels to rise. Then they should gradually add complex carbohydrates.

Blum recommends the use of the artificial sweeteners sucralose and saccharine for people with insulin resistance and diabetics, but not aspartame, which she says can cause complications in people with the genetic condition of phenylketonuria and interfere with the secretion of insulin. In addition, when heated over 30ºC, says Blum, aspartame can turn into methanol, which is toxic and can cause muscle or joint pain. However, these symptoms pass when one stops consuming aspartame.

Women who carefully followed their assigned diets lost an average of four kilos monthly, while men lost five. The lower the serotonin level before the diet, the better the improvement in moods after the diet was followed. If people with high serotonin legvels ate a high-carb diet – against Blum’s advice – they reported anxiety and discomfort due to excess serotonin.

She maintains that the dropout rate from her diets are much lower (only 20% to 30%) compared to 70% from other diets, such as Atkins and South Beach, which are much more extreme and not based on the principles she promotes.

Only patients with serious weight problems should consider asking a doctor for medications that reduce appetite or increase satiety; the same goes for those who want bariatric surgery to constrict their stomach or intestines. But Chapter 18 strongly endorses regular exercise and explains its beneficial effects on weight loss and mood improvement due to the endorphins produced by physical activity.

Blum repeatedly urges readers – both those who are healthy and those with chronic illness – to consult their physicians and clinical dietitians before adopting a diet based on  serotonin levels.

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