Faculty of Allied Health Sciences > Nutrition and Food Engineering

Exploring Metabolism in Starvation

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nfe fouzia:
We often get sick of reading responses of people regarding diet and weight loss with everyone throwing around purported "facts" about starvation mode. So, here is a little research on the topic. Feel free to chime in with other studies, but lets keep it based on actual research, not personal anecdotes and not "my trainer says."

Starvation mode does not happen overnight or even in just a few days! Calories in, calories out. Simple, right? Short term, yes, it’s simple, long term, not so much. Let’s add some real science to the discussion:

First, a definition. Starvation mode does not mean going without food. It means that you cut your caloric intake to less than what the body would normally burn in the course of a day. I have seen so many posts where people offer advice and tell people they need to eat more to lose weight because they are starving their bodies. The idea postulated is that eating too few calories will reduce a person’s metabolism to such an extent that the person will gain weight instead of losing.

nfe fouzia:
Now, a look at one of the classic scientific studies on starvation. Probably the most famous study done was conducted after WWII by researchers at the University of Minnesota. Starvation was widespread throughout Europe during the war and scientists were trying to figure out how to re-feed people suffering from starvation and determine the long-term effects. (Remember, tens of thousands of people died after liberation from concentration camps not only from disease but from the reintroduction of food that their bodies were no longer capable of digesting.) Scientists recruited 36 young healthy men to participate in a yearlong study divided into several phases: a 12-week normal control period, a 24-week starvation phase where calories were so dramatically reduced that participants lost approximately 25% of body weight; and, finally, a recovery phase to renourish participants. Results of the study were published in the two-volume, Biology of Human Starvation (Minneapolis: University of Minneapolis, 1950).

nfe fouzia:
So, what did the results of the study find? First, all participants lost weight. Starvation mode does not result in your body hanging onto extra fat or calories in an effort to “preserve” your body. But, it’s more complicated than just losing weight. All of the participants also experienced a drop in their metabolic rates – approximately 40% below baseline. Now, you will see many posters here that will argue that you will start losing muscle and not fat within a few days of going into so-called “starvation mode.” Yet, the research shows that participants lost both. In fact, at no point did they stop losing fat until they hit a rate of approximately 5% body fat near the end of the study.

nfe fouzia:
Lyle McDonald explains it this way:

In general, it's true that metabolic rate tends to drop more with more excessive caloric deficits… But here's the thing: in no study I've ever seen has the drop in metabolic rate been sufficient to completely offset the caloric deficit. That is, say that cutting your calories by 50% per day leads to a reduction in the metabolic rate of 10%. Starvation mode you say. Well, yes. But you still have a 40% daily deficit.

But, keep in mind that apart from weight loss, semi-starvation has other not-so-cool effects on your mind and body. The other physical effects from the Minnesota study on semi-starvation included a significant drop in physical endurance, reduction in strength of about 10%, and sluggish reflexes. Those that were the most fit initially showed the greatest deterioration. In addition, heart volume shrank about 20%, pulses slowed and their body temperatures dropped. Concentration and judgment became impaired. Sexual function was reduced and all lost interest in sex. They had every physical indication of accelerated aging. But keep in mind, this was a year-long study, not something that happened in a just a few days or two weeks of eating restricted calories.

nfe fouzia:
The more dramatic effects of semi-starvation from the Minnesota study were psychological, similar to what can be observed in anorexic patients. The men became nervous, anxious, apathetic, withdrawn, impatient, self-critical, emotional and depressed. A few even mutilated themselves, one chopping off three fingers in stress. They became obsessed with food, thinking, talking and reading about it constantly; developed weird eating rituals; hoarding, etc.

Now, let’s look at another aspect. The folks at Cambridge University in England did a study to determine the different effects starvation had on lean people versus obese people. The study can be found here: http://www.unu.edu/unupress/food2/UID07E/uid0 7e11.htm. Let’s just cut to the chase with this study.

Does starvation mode slow down the metabolism? No and Yes.

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