Posts Tagged ‘obesity’

Using Our Minds to Control Our Eating

March 9, 2013

Obesity is a worldwide problem now, and dieting is a personal problem for many of us. It appears that both evolution and the food industry has conspired to make us desire fattening foods. Consequently, dieting is difficult. Are there any good techniques for controlling our eating? The answer is, yes. One of these techniques is our mind. Mindfulness can help us control our eating.

An experiment1 investigated whether eating lunch mindfully, in contrast to eating with distractions or no particular focus, reduced later snack intake. Twenty-nine female undergraduates either ate a fixed lunch while (1) focusing on the sensory characteristics of the food as they ate (food focus group), (2) reading a newspaper article about food (food thoughts control group), or (3) in the absence of any secondary task (neutral control group). Later in the afternoon cookie intake was measured as well as rated vividness of memory for lunch. Participants in the food focus group ate significantly fewer cookies that participants in both the food thoughts control group or the neutral control group. Rated appetite before the snack session was lower in the food focus group than in the other two groups. Their rated vividness of their memory of lunch was higher in the food focus group. The rated vividness of lunch memory was negatively correlated with snack intake.

This study strongly suggests that memory plays an important role in appetite control. Paying attention to food while eating enhances this meal memory.

So to control our appetites we should not eat while we are either watching television or reading. Moreover, if we concentrate on the meal and the enjoyment of the meal, our subsequent hunger and desire for snacks will lessen. Conversation remains an open issue. Conversation typically slows down our consumption of food, but if it takes our minds off what we are eating, it might be problematic. Perhaps its best to work comments about the meal into our conversations.

1Higgs, S., & Donohoe, J.E. (2011). Focusing on food during lunch enhances lunch memory and decreases later snack intake. Appetite, Aug57(1):202-6. Doi: 10.1016/j.appet.2011.04.016. Epib2011 May4.

© Douglas Griffith and, 2012. Unauthorized use and/or duplication of this material without express and written permission from this blog’s author and/or owner is strictly prohibited. Excerpts and links may be used, provided that full and clear credit is given to Douglas Griffith and with appropriate and specific direction to the original content.

Can Memory Affect Obesity?

January 12, 2013

M is an individual who has had part of his memory removed, that part likely including the hippocampus, in an attempt to cure epilepsy. Sixty seconds after polishing off a three course meal, he started on a second three course meal having forgotten the three course meal he had already eaten. This finding was replicated with two other individuals who had undergone the same surgery. Not only did these two people eat a second meal fifteen minutes after eating the first, but sometimes went on to eat a third meal.

It appears that their amnesia has caused these individuals to forget they that have eaten, but not entirely as recent research has identified sensory specific satiety. We are familiar that our liking for a specific food decreases the more we eat of it, whereas a different dish can be more appetizing. People with the described amnesia will prefer crisps or cookies rather than more sandwiches after eating a hearty lunch of sandwiches even though they cannot remember what they have just eaten.

Research has also shown that imagining the process of eating something can lead us to feel more satiated such that we eat less. So memory does affect our appetites and our appetites affect obesity. Moreover, we can call upon our memories to help us imagine something tasty that we have eaten. For this to be effective, it is important that it be done slowly and with sufficient imagination to closely recreate the sensation of eating. Imagine whatever you like as calories do not count in a bad way when your eating is imaginary. It is even possible that the more calories you are imagining the more effective this memory ruse might be.

De Lante, C. (2012). Stuck in the Present. New Scientist, 6 October, p.41.

© Douglas Griffith and, 2012. Unauthorized use and/or duplication of this material without express and written permission from this blog’s author and/or owner is strictly prohibited. Excerpts and links may be used, provided that full and clear credit is given to Douglas Griffith and with appropriate and specific direction to the original content.

You Have Two Brains

December 26, 2012

As do I. It was described by Byron Robinson in The Abdominal and Pelvic Brain in 1907 and named the enteric nervous system (ENS) by Johannis Langley.1 About the same time it was found that the ENS can act autonomously. When its main connection with the brain, the vagus nerve, is severed the ENS still is capable of coordinating digestion. Interest in this gut brain dropped until the field of neurogastroenterology was born in the 1990’s. It has since been learned that about 90% of the signals passing along the vagus nerve come not from the brain above, but from the ENS.2

How do these two brains compare? Both have barriers restricting blood flows to their respective brains and are supported by glial cells. The first brain consists of about 85 billion neurons; the second brain has about 500,000 neurons. 100 neurotransmitters have been identified for the first brain; 40 neurotransmitters have been identified for the second brain. Each brain produces about half of the body’s dopamine. The first brain produces 5% of all serotonin. The second brain produces 95% of all serotonin. This final comparison is quite telling. Serotonin is best known as the “feel-good” molecule. It is involved in preventing depression and in regulating sleep, appetite, and body temperature. Serotonin produced in the gut gets into the bloodstream, where it plays a role in repairing damaged cells in the liver and lungs. Moreover, it is important for the normal development of the heart, as well as in the regulation of bone density by inhibiting bone formation.

Serotonin produced in the ENS affects mood by stimulating the vagus nerve. Research has shown that stimulation of the vagus nerve can be an effective treatment for chronic depression that has failed to respond to other treatments.3 These gut to brain signals via the vagus nerve might also explain why fatty foods make us feel good. Brain scans of volunteers given a dose of fatty acids directly into the gut had a lower response to pictures and music designed to make them feel sad that a control group given saline. The fatty acid group also reported being only about half as sad as the control group.4

Stress leads the gut to increase its production of ghrelin. Ghrehlin is a hormone that makes you feel hungrier as well as reducing anxiety and depression. It stimulates the release of dopamine in the brain both directly, by directly triggering pleasure and reward pathways, and indirectly by signals triggered via the vagus nerve. At one time during our evolutionary past, the stress-busting effect of ghrelin might have been useful, but today the result of chronic stress or depression can be chronically elevated ghrelin leading to obesity.

The second brain has also been implicated in a variety of first brain disorders. In Parkinson’s disease the problems with movement and muscle control are caused not only by loss of dopamine producing cells in the first brain, but also by dopamine producing cells in the second brain due to Lewy bodies. It is even suspected that the disease starts in the second brain as the result of some trigger such as a virus, and then spreads to the brain via the vagus nerve. Similarly the characteristic plaques and tangles found in the first brains of people with Alzheimer’s are present in their second brains also.

Cells in the second brain could be used as the basis for treatments. One experimental intervention for neurodegenerative diseases involves transplanting neural stem cells into the first brain to replenish lost neurons. Harvesting these cells from the brain or spinal cord is difficult. Neural stem cells have been found in the second brain of human adults.5 These cells could be harvested using a simple endoscopic gut biopsy. This could provide a ready source of neural stem cells. One research team is planning toed them to treat diseases including Parkinson’s.

1Young, E. (2012). Alimentary thinking. New Scientist, 15 December, 39-42.

2American Journal of Gastrointestinal and Liver Physiology, vol 283, p G217.

3The British Journal of Psychiatry, vol 189, p.282.

4The Journal of Clinical Investigation, vol 121, p. 3094.

5Cell Tissue Research, vol 344, p.217.