It appears that weight regain is the typical long-term response to dieting, rather than the exception – Traci Mann Prof Psychology.

Why?

Is it because they are too weak-willed to continue restricting their food intake? Is it because their body physiologically defends a genetically-based set weight?

The answer is a combination of both and is easily misunderstood:

In short

Calorie deprivation leads to changes in hormones, metabolism, and cognitive/attentional functions that make it difficult to continue with the behaviours needed to keep weight off.

Possible Causes

1. HORMONES

An ever-expanding list of appetite-mediating hormones includes leptin, ghrelin, cholecystokinin, peptide YY, insulin, pancreatic polypeptide, glucagon-like peptide-1, etc.

These hormonal signals are integrated by the Hypothalamus, the Commander in Chief which is also Commander in Chief for various neuroendocrine (hormone) axes including the HPT hypothalamic-pituitary-thyroid axis and the HPA hypothalamic-pituitary-adrenal axis.

These axes also contribute to body weight homeostasis through hormones like Thyroid and Cortisol, even Estrogen and Testosterone

No surprise that this neuroendocrine milieu is profoundly altered first in response to Obesity and then to weight loss.

Therefore

Individuals in a deprived state experience more hunger, and feelings of hunger remain increased for deprived individuals even after eating a regular meal.

2. METABOLIC EFFECT

A reduction in energy expenditure / the amount of energy burned. Less energy is needed to “run” the smaller body. A decrease in energy expenditure is known as “adaptive thermogenesis”.  

Metabolism becomes more efficient, allowing the body to survive on less energy than similar sized bodies that were not calorie deprived.

Therefore, to continue losing weight, the individual must consume even fewer calories than during the initial stages of the diet.

Energy restriction and weight loss is believed to involve a shift in metabolism that favours fat burning over carbohydrate, with weight regain coinciding with a metabolic reversal back to carbohydrates.

Thus, a low carbohydrate diet may protect against weight regain by blocking this metabolic reversal. Cortisol levels increase markedly with energy restriction which increases weight gain. Stress increases Cortisol and weight gain, especially central fat storage.

3. GUT FUNCTION

Delayed gastric / stomach emptying in obesity may actually promote feeding through delayed delivery of nutrients to the duodenum and the associated release of satiety hormones.

Recently, new evidence has emerged that this may contribute to weight regain in obese patients

An association between the gut microbiota and obesity has been identified, such as overweight/obese humans have low bacterial diversity, fewer different types of bacteria

Gut microbiome influences how food is digested and absorbed and how dietary fats are stored in your body.

Gut microbiome may also impact the production of hunger hormones, such as Ghrelin, which control if you feel hungry or full

Mechanisms by which gut microbiota promote metabolic disturbances are not well understood. Leading theory is changes in molecular signaling chemicals / hormones released by bacteria in contact with local tissue or distant organs

Bacteroidetes prevalence is lower in obese people, and Firmicutes phylum increased associated with elevated energy harvesting from the diet

Lactobacillus and Clostridium species are associated with insulin resistance, both Firmicutes

The microbiota has effects way beyond the gut. Adipose tissue / fat cells are a primary target making fat cells resistant to insulin

This increases fat released into the blood stream which is sequestered by other organs (liver and skeletal muscles) that are not equipped to safely store excess fat

Multiple studies link gut dysbiosis to obesity related liver disease. Non-Alcoholic Fatty Liver Disease presents with intestinal-bacterial overgrowth and enhanced intestinal permeability.

Artificial sweeteners can change beneficial bacteria in your gut

4. PSYCHOLOGY

• Due to lack of stimulation in the Hypothalamus people’s attention is biased toward food stimuli when they are calorie deprived
• They have heightened food smell functioning
• They have heightened food tastes
• They have heightened drive to consume food

5. TIME

• Effects of calorie deprivation last a long time.
• Overly efficient metabolic rates and preoccupations with food can last a year or more after a starvation period has ended
• After 10 weeks of dieting satiety hormones like Leptin measured at week 10, and again at week 62 measured significant and persistent reductions in levels of leptin, peptide YY, cholecystokinin, and insulin and increases in levels of ghrelin and pancreatic polypeptide.
• All of these hormonal changes are believed to be permissive of weight regain and increased appetite.
• Strong linear correlation between the decreases in Leptin and weight regain.
• A significant decrease in Leptin levels following weight loss of over 5%, but not below 5%,
• Contestants on the “The Biggest Loser,” who lost an average of 128 pounds in 30 weeks, still maintained a ‘disturbed’ metabolism even six years later

Solutions

• Be patient and persistent
• It takes a LONG time to reset metabolism

Change focus

• Focus on gut health
• Focus on health rather than weight / diet
• Education regarding foods
• Stop / limit unhealthy habits, such as smoking alcohol, excess glucose and processed carbs, late nights
• Increase healthy habits, no food after 6pm, exercise / movement 30 mins every day, bed by 10pm
• Keep a diary or log of your progress.