When we talk about dieting, we need to clarify our levels. Generally, we need a certain amount of calories every day. Even when you are lying on your couch eating, your body is slowly burning calories. You can figure out how many by using a BMR (basal metabolic rate) calculator.
Now, my BMR is a lovely 2800 calories. That’s me sitting all day, no exercise. But I can tell you that when I don’t eat that number of calories, my weight doesn’t just drop away. (See the gruesome peanut butter and celery diet I did last month). Instead, that BMR is based on a thermostat of 98.6 degrees. If you don’t have enough fuel, your body automatically turns down the thermostat and you get colder, not thinner.
Here’s where the fun comes in. If you take away all the fuel, you will start dropping weight. Yes, starvation works short term, but at a terrible cost. You eat yourself, including muscles. This is where the whole high protein diet comes in, trying to protect your muscles while you drop fat. I’ve never seen muscle biopsies done before and after to judge if that food selection is effective at muscle sparing.
But starvation also sets up a whole different level of fun if you start eating again. Now all your hormones will be on storage mode. We are set up to defend against future starvation, so now you’re monkeying with the central mechanisms. Chances are really high that the basic functions of your brain are going to interpret your stress about food as stress about starving, not as stress about wanting to look starved.
But let’s just think about the next twelve weeks of dieting for a moment. You’re better off starving (under medical supervision) than you are dieting fiercely for twelve weeks. Don’t believe me. Here’s the study.
For the metric impaired (which includes me) here are the conversions: 5000kj is about 1200 calories, 6000 kj is 1400 calories. The starving group got 3000 kj or roughly 700 calories.
Let me put this into context: In the definitive study on starvation “during the 6-month semi-starvation period, each subject’s dietary intake was cut to approximately 1,560 calories per day.” If you look at that text, the subjects experienced severe issues on that caloric intake. Nowadays, we think it is reasonable to halve that caloric intake.
Intentional weight loss with a reduction in adipose tissue is associated with an improvement in medical complications linked to obesity. The aim of this study was to compare the effect of two different weight loss diets on obese individuals (BMI 30-40 kg m(-2)) for improvements in anthropometric measurements and blood biomarkers. Study 1 comprised a low energy diet (LED) of 5000-6000 kJ d(-1) for a slow but steady weight loss over 12 weeks. Study 2 comprised a very low energy diet (VLED) of 3000 kJ d(-1) using meal replacements for rapid weight loss over a shorter period of 4 weeks followed by 10 weeks of weight stabilisation to prevent rebound after rapid weight loss. Nutrition information sessions were given to both groups. Fasting blood samples, anthropometric measurements and 3-day food diaries were collected at baseline and again at completion of weight loss, at 12 weeks for LED group and 4 weeks for VLED group. Mean weight loss in the LED group (n = 18) was -3.17 kg (-3.7%) compared to a -6.54 kg (-7%) loss in the VLED group (n = 14) (p < 0.001). The VLED group experienced significantly greater reductions in fat mass, -13.9% compared to -8.9% for the LED group (p < 0.05). Significantly greater reductions in blood glucose (p < 0.05), cholesterol and LDL-C (p < 0.01 for both), and waist circumference (p≤ 0.05) were noted in VLED compared to those for LED diet. Short-term, rapid weight loss produced the desired ≥5% weight loss suggested to substantially reduce metabolic abnormalities associated with obesity, and to reduce health risks.
- PMID: 21922120