Saturday, September 25, 2010

Is eating 6 meals a day instead of 3 a better weight loss strategy?

I’ve come across a significant number of non-peer reviewed articles on the internet about weight loss, body building etc. that advocates eating 6 meals a day (just Google "3 meals or 6 meals" to see what I mean). Reasons given for doing so includes less fluctuation in blood glucose and lower fat storage among others. But is eating 6 meals instead of 3 a day really beneficial for someone trying to cut some flab? Some researchers think not.

In an article published in Obesity, Leidy and colleagues (2010) investigated how differing amount of dietary protein and eating frequency influences our perceived appetite and satiety levels during weight loss. 

In a 12 week experiment, 27 obese men were randomized into either the high protein or normal protein group and were required to engaged in a weight-loss diet that is 750kcal/day lower than their daily needs. Beginning on the 7th week, all participants alternated between 3 meals a day or 6 meals a day, each lasting for 3 days. Information on their perception of daily hunger, desire to eat and thinking about food were recorded and compared.

  • The high protein group felt fuller, had lower desire to snack at night and thought less about food than the normal protein group.
  • Eating 3 or 6 meals a day did not have any effect on hunger, fullness, desire to eat nor preoccupation with thoughts of food.

The take-home message? Getting on a high protein diet appears to be a viable weight loss strategy because it gives you better control over your appetite and satiety but switching to a 6 meals a day strategy appears not to be helpful in these areas.

Furthermore, some previous studies have found a relationship between higher meal frequency and higher colon cancer risk (eg. Shoff et al, 2000 (for women), Wei et al. 2004(for men)). So I were you, I'll think twice about adopting that 6 meals a day plan too readily.
Leidy HJ, Tang M, Armstrong CL, Martin CB, & Campbell WW (2010). The Effects of Consuming Frequent, Higher Protein Meals on Appetite and Satiety During Weight Loss in Overweight/Obese Men. Obesity (Silver Spring, Md.) PMID: 20847729
Wei, J., Connelly, A., Satia, J., Martin, C., & Sandler, R. (2004). Eating Frequency and Colon Cancer Risk Nutrition and Cancer, 50 (1), 16-22 DOI: 10.1207/s15327914nc5001_3
Shoff, S., Newcomb, P., & Longnecker, M. (1997). Frequency of eating and risk of colorectal cancer in women Nutrition and Cancer, 27 (1), 22-25 DOI: 10.1080/01635589709514496

Saturday, September 18, 2010

Spicy food and collectivism: How the brain shapes culture

We are used to thinking of culture as a social factor and not a biological factor. We attribute dispositions such as being individualistic or being collectivist to the country that one was brought up in, but no one has really looked into why certain cultures tend to be that way. An emerging field of research called cultural neuroscience says that cultural values can be shaped by the brain and genes.

For example, in one striking example I read about quite recently, one hypothesis put forth for the reason why Asian people like spicy food was because spices conferred natural bacteria killing properties that was especially important in a humid climate where food went bad. Over time, the hypothesis goes, people who liked spicy food more and ate more spicy food were less prone to stomach diseases that killed the others, thus passing on their genes for the next generation. A similar finding was found when examining lactose intolerance. Lactose intolerance is far more prevalent in certain regions of Asia where the rearing of lifestock for milk is less common. In Europe however, up to 95% are able to digest lactose, and this is reflected in their preference for milk products like cream and cheese.

In this review by Way and Lieberman, they sought to answer the question as to why certain cultures tend towards individualism and collectivism. They reason that because of evolution, genes that change brain function and influence the cultural norms we adopt and we institute are selected for between people born in different regions. For people brought up in one region that was say marked by famine, grouping together and helping one another might have brought about greater survival for the people, hence the genes that promote this thinking get passed on. In a separate part of the world, marked by conflict perhaps, survival would favor people who think for themselves and for their immediate family members. Over time, those different selective pressures would have promoted different social behaviors in different regions.

What mechanisms might have promoted these behaviors? They reviewed work from scientists studying the distribution of several genetic alleles. Previous work has shown that variation in the serotonin transporter gene, a very important neurotransmitter associated with emotion and reward, was associated with individual differences in social sensitivity. People with the short version show greater reaction to social events such as death or birth of children, regardless of whether it was positive or negative. When these scientists studied the distribution of these alleles in different cultures, surprise surprise! They found that the short version of this allele was much more prevalent in collectivist cultures than individualist cultures.

*higher score on individualism collectivism scale indicates higher individualism.

The authors hypothesize that since this allele makes people more sensitive to being socially excluded, it promotes individuals to tend and befriend, leading to a cultural trend of being more collectivist. There's more to read about other such alleles in the review, but seeing as to how this post is quite wordy already, I'll stop here :)

ResearchBlogging.orgSherman, P., & Billing, J. (1999). Darwinian Gastronomy: Why We Use Spices BioScience, 49 (6) DOI: 10.2307/1313553

Way, B., & Lieberman, M. (2010). Is there a genetic contribution to cultural differences? ... SCAN, 5 (2-3), 203-211 DOI: 10.1093/scan/nsq059

Wednesday, September 8, 2010

Why does Time Slow to a Crawl when we Engage in Laborous Tasks?

"Put your hand on a hot stove for a minute, and it seems like an hour. Sit with a pretty girl for an hour, and it seems like a minute."

- Albert Einstein, on Relativity.

Kathleen Vohs and Brandon Schmeichel, particularly fascinated with Einstein's first observation, sought to establish whether regulating the self can elongate the 'felt' duration of time. "Because people who are self-regulating tend to monitor their behaviour, they are likely to be attuned to the passage of time," explain the authors, "these monitoring responses and resultant attention to time are not found among people who are not regulating."

In simpler terms, 'self-regulation' is likely to be linked with the attention to time. In earlier studies on duration judgment, when participants were asked after watching a TV episode to estimate the length of the episode, they gave shorter time estimates than participants who were told that they had to guess the duration of the episode prior to watching it. It appears that conscious deliberation, as opposed to the non-regulated state of automatic processing, might lead one to be more aware of time passing.

Thus, hypothesizing that deliberate, conscious and effortful self-regulation would lead one to feeling like time has passed slowly, Vohs and Schmeichel conducted four illuminating studies that lent scientific support to the claim.

In Study 1, the authors made participants watch a clip from the film Terms of Endearment, which shows a dying mother saying good-bye to her children, husband and mother. Participants were made to either naturally respond to what they saw, or suppress their emotions or exaggerate their emotions while watching the show. This manipulation had been found in earlier studies to be effective in causing participants to consciously regulate their emotions which led to diminished self-control capacity.

Participants were instructed to estimate the length of the video clip after the 11 min 23 sec clip ended.

It was found that participants who exaggerated or suppressed their emotions perceived that the film clip had lasted longer than participants who were natural during the film.

In Study 2, a similar experimental set up was used, although the film was changed from Terms of Endearment to Mondo Cane (depicting the death of wildlife). To determine that longer judgments of time were due to self-regulation specifically and not generic information processing, a new condition called 'reappraisal' was introduced. Participants in the reappraisal group were instructed to view the affectively-charged scenes in a detached manner. The authors explain: "Prior studies have shown that effects associated with emotion control (e.g. memory decrements because of emotion suppression) are absent when participants are given a reappraisal framework within which to view an emotional scene."

Participants were, again, then asked to judge how long the clip lasted.

The results support the idea that the Natural and Reappraisal conditions, which did not require self-monitoring, did not prompt the attention to time that was present in the Suppress condition.

In Study 3, participants were told to read aloud pages of text that corresponded to various types of professions. In the behavioural control group, participants were instructed to 'act out' the profession as depicted by the text, and thus they had to do their best to "act happy, smile and 'get into it'" as expected of the profession. Participants in the no condition group weren't given any such instructions.

After 4 minutes and 23 seconds had passed, participants were interrupted with a questionnaire asking them how long they thought the experiment had lasted. After that, participants were told that they could continue up to a cap of 15 minutes and stop at anytime in between.

Once again, the findings of the first two studies were replicated in the results of Study 3 as participants in the behavioural control group felt that they spent a longer time doing the task than participants in the no condition group. Continuance of the task was also affected by the manipulation, as "the longer participants believed they had been doing the read-aloud task, the shorter they continued with it after the 4:23 mark."

From this, the authors built a model that linked the experimental conditions and subsequent regulatory ability.

The results of this model were supportive of the hypothesis that time perception is a mediator. This model was further supported by a final study.

Thus, across four experiments, the authors found that people's perceptions of the duration of an activity were significantly affected by self-regulatory resource depletion. Whenever some form of cognitive regulation is involved, for instance, emotion regulation or self regulation, people can believe that the task involved lasted much longer. "A taxing self-regulatory activity is remembered as being overly long."

Where Einstein's latter observation is concerned, it might thus be likely that sitting with an attractive member of the opposite sex constitutes a very enjoyable process that requires less self regulation, which makes us less conscious of the passage of time. So, where does this place those who experience anxiety approaching attractive members of the opposite sex?

This post was chosen as an Editor's Selection for
Vohs, K., & Schmeichel, B. (2003). Self-regulation and extended now: Controlling the self alters the subjective experience of time. Journal of Personality and Social Psychology, 85 (2), 217-230 DOI: 10.1037/0022-3514.85.2.217