Weight Regulation: Do Calories In = Calories Out?
In our culture, dieters are taught to use willpower and self-deprivation. Failure to lose weight or maintain weight loss is associated with traits such as weakness, lack of self-control, poor will power, poor motivation and hopelessness. But hunger and metabolic rate are not under conscious control.
Our weight is hormonally regulated and metabolically controlled. The hypothalamus regulates the homeostatic control of food intake via hormonal feedback as well as input from the cortex (reward system) and limbic system (social and emotional factors that impact eating patterns). In the fed state, we secrete hormones such as leptin, peptide YY, amylin, cholecystokinin and the incretin hormones; glucagon-like peptide -1 (GLP1) and gastric inhibitory peptide (GIP). These hormones trigger a reduction in hunger (resulting in a reduction in food intake) and an increase in energy expenditure. In the unfed state, we secrete hormones such as ghrelin, which trigger hunger, and our metabolic state shifts towards conservation of energy.
Is current dietary advice correct? Does calories in = calories out?
Let’s talk about the 1944 “Minnesota Starvation Study” published in 1950 “The Biology of Human Starvation.” This study consisted of 36 young fit healthy male university students and was divided into three phases
Phase one: participants were fed a standard American diet with a calorie intake of about 3200 calories per day. Calories where were mostly obtained from carbohydrates sources, such as potatoes, bread and pasta. This diet is very similar to the current diets followed in Australia and America.
Phase 2: Caloric intake was reduced to ~1550 calories/day, with adjustments in caloric intake as participants lost weight to target a total weight loss of 25%. Some participants had intakes restricted to <1000 calories per days.
Phase 3: participants were refed the standard diet in phase 1.
What were the outcomes?
Phase 1: No measurable changes were noted.
Phase 2: participants lost a significant amount of body weight. However, no one met the target weight loss of 25% of their initial body weight. Instead, their resting metabolic rate (BMR) dropped by 40%; they lost muscle mass and physical endurance; their heart rates and body temperature dropped; their hair fell out. One hundred percent of participants experienced severe cognitive effects such as depression and anxiety; fatigue; cognitive fog; complete lack of interest in everything except for food, which they became intensely preoccupied with.
Phase 3: Participants quickly regained body weight, and almost all of the measured physiological parameters (above) returned to normal apart from their BMR, which remained suppressed despite restoration of weight. Weight continued to climb until all participants were above their initial weight. Participants also continued to display abnormal eating behaviours with loss of control and binge eating
The “Minnesota Starvation Experiment.” Published in 1950 in a two-volume report “The Biology of Human Starvation” by the University of Minnesota Press.
The “Biggest Loser study” is a modern-day version of the Minesoda starvation study. This study followed participants from the popular television program, “The Biggest Loser” which was based on calorie restriction and increasing physical activity. The study followed participants for a period of six years after completion of the program. Six years later, most participants had regained the weight lost in the program and showed ongoing and significant reductions in BMR.
Fothergill, et.al. Persistent metabolic adaptation 6 years after “The Biggest Loser” competition. Obesity; 2016; 24 (8); 1612-1619.
When we calorie restrict, our bodies shut down to conserve energy and prolong survival. In other words, caloric reduction doesn't work for effective or sustainable weight loss. This is because, our weight is hormonally regulated and metabolically controlled.
Now let’s look at another situation where calories are abundant, but carbohydrates are restricted. In a case series presented by Dr Jessica Turton at a previous Low Carb Down Under (LCDU) conference, participants were recruited because they were failing to lose weight or maintain weight loss while participating in a weight loss program. This program was based on a calorie restriction model, with restrictions of about 1400 calories per day (note this is less than that seen in stage 2 of the Minnesota Starvation Study). Dr Turton’s study involved restricting carbohydrate intake while providing abundant calories in the form of fat and protein, which amounted to an intake of around 2190 calories per day. Participants were followed for around 61 week and despite almost doubling caloric intake, an average weight loss of around 10kg was observed over this period.
We are also advised to increase exercise to lose weight. Exercise is critical in maintaining physical and psychological health. It is also essential to for protecting lean muscle mass and bone density when moving towards intermittent fasting. However, studies have demonstrated that if we increase energy expenditure in the form of exercise, two events occur:
We increase energy intake to match the additional energy used during exercise. For example, if we go for a swim in the morning, then we are more likely to have a larger breakfast, because we are hungrier.
We reduce our energy expenditure at other time of the day. For example, if we go for a swim in the morning, we are more likely to watch TV or go to bed early rather than vacuum, or mow the lawn because we are tired.
Weight is hormonally regulated and metabolically controlled. Obesity is a chronic disease not a lifestyle choice.
