Starvation Mode: Risks of Undereating after Bariatric Surgery

Article By: Rachel Ignomirello, MS, RDN, CSOWM, LDN

Rachel Ignomirello is a Bariatric Dietitian and Board-Certified Specialist in Obesity and Weight Management.

Metabolic and bariatric surgery decreases the amount of food a person can consume at one time and reduces nutrient absorption. Patients experience significant weight loss and countless health benefits as a result of this procedure. Despite the life-changing improvement, our bodies do not always see it that way.

1) What is starvation mode?

Basal metabolic rate (BMR) measures the calories your body needs to perform vital functions like heart rate and breathing. BMR is calculated using height, age, sex, and weight. When weight (fat and muscle) loss occurs, the body lowers its BMR to make up for that loss. If you have less overall mass, you need fewer calories to support that mass.

It’s like slowing down your spending because you discover your bank account has a low balance. This adjustment happens because the body wants to maintain energy balance and have enough fat stores to survive a hypothetical famine. This metabolic adaptation is called adaptive thermogenesis but is more commonly referred to as “starvation mode.” It’s a normal physiological response to reduced calorie intake and weight loss.

2) Does this prevent weight loss?

Starvation mode is real but not as powerful as people think when it comes to preventing weight loss. Currently, research suggests that it happens but that it doesn't play a significant role in weight regain. As you lose weight, you do need fewer calories. This is why weight loss slows over time and why it’s so difficult to maintain weight loss on your own. People must eat fewer calories forever and maintain behavior change to continue losing weight. Having a period of weight stabilization may help BMR recover to lessen the effects of starvation mode.

3) What are the risks of under-eating?

Starvation mode is really a misleading term. Actual starvation is long-term nutrition deprivation. An extended period without food or with very limited food will leave the body with an excessively large calorie deficit. Out of desperation, many people have resorted to “starving” themselves of calories. This practice is not healthy and is not sustainable for someone that underwent bariatric surgery. The body does not function well, mental health worsens, and metabolism may be altered. In fact, it can even lead to organ damage or death. Patients report more fatigue and difficulty doing everyday tasks. Under-eating can lead to malnutrition, which is a condition from a lack of calories, protein, and/or micronutrients (vitamins and minerals). Because the body tries to compensate, people often experience changes to hair, skin, and nails. Bariatric patients can experience some nutritional deficiencies after weight loss surgery and can be at even higher risk for malnutrition if they are skipping meals, not getting enough protein, and/or not taking their vitamins.

4) Can metabolism be boosted?

Patients often experience quick results when they start on their weight loss journey. Progress often does slow over time – sometimes to the point where the scale does not move for weeks. Despite having the drop in BMR from weight loss, it does not happen overnight and won’t last forever. Although this metabolic adaptation is inevitable, there are some tricks to boost it. Rapid weight loss can reduce muscle mass, but resistance exercise (strength-training) can help fight it.

In a study of women, there were three groups on a very-low calorie diet. One group did not exercise, another only did aerobic exercise (cardio), and the last group did resistance exercise. The resistance group members were the only ones who maintained their muscle mass, strength, and BMR. To no surprise, protein is important for muscle. The body is less inclined to break down muscle for energy if protein intake is elevated. This preserves muscle mass and may slow the natural metabolic slowdown. When patients exercise and get enough nutrition, there are improvements in energy and body composition, which in turn can improve activity and weight loss.

BariMelts provides general recommendations, not to be construed as medical advice. Please consult your doctor.


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