Amyotrophic Lateral Sclerosis (ALS) is a progressive neurodegenerative disease affecting nerve cells in the brain and spinal cord, leading to the loss of muscle control. While a recognized symptom of ALS is weight loss, a less common phenomenon is weight gain. This article explores why weight gain can occur in some individuals with ALS and what it signifies for managing the condition.
The Paradox of Weight in ALS
Weight loss is a frequent symptom in ALS, associated with a faster progression of the disease. A primary cause is hypermetabolism, a state where the body’s resting energy expenditure is higher than normal, causing it to burn calories at an accelerated rate. Studies have shown that about 50% of people with ALS are hypermetabolic.
Another factor is dysphagia, or difficulty swallowing, which arises as the muscles for chewing and swallowing weaken. The physical act of eating can become exhausting due to generalized weakness and fatigue. Muscle atrophy, the wasting away of muscle tissue from nerve degeneration, also directly reduces overall body mass.
Causes of Weight Gain with an ALS Diagnosis
Despite the prevalence of weight loss, some individuals with an ALS diagnosis experience weight gain. A primary reason is the use of a percutaneous endoscopic gastrostomy (PEG) tube. These feeding tubes prevent malnutrition when swallowing becomes unsafe, but the high-calorie formulas can provide more calories than the body expends if not precisely calibrated to metabolic needs.
Reduced physical activity is another contributor. As ALS progresses, mobility becomes limited, decreasing daily energy expenditure. If caloric intake remains stable or increases, especially with tube feeding, the unburned calories are stored as fat. This is common in advanced stages with severely restricted movement.
In some cases, weight gain may result from fluid retention (edema), as immobility can cause fluid to pool in the legs and feet. Certain medications, such as steroids, can also have weight gain as a side effect. Some people may also perceive weight gain around their waist that is actually a result of lost abdominal muscle tone.
Implications of Weight Gain for Disease Management
Research has identified an “obesity paradox” in ALS, where maintaining a stable body mass index (BMI) in the slightly overweight or obese range (30-35 kg/m2) is associated with slower disease progression. Having energy reserves can be protective, as a lower BMI is linked to poorer outcomes. For this reason, avoiding weight loss is a primary goal in ALS care.
However, excessive or rapid weight gain is not beneficial and can create new challenges. Increased body weight places a greater burden on the respiratory system, which is already compromised by weakening muscles. This can make breathing more difficult and may accelerate the need for respiratory support.
Excess weight can also make mobility and transfers more difficult for the individual and their caregivers. It can heighten the risk of developing pressure sores, as there is more weight compressing the skin over bony areas with prolonged immobility. The focus is on maintaining a stable weight, rather than continuous gain.
Nutritional Strategies for Weight Stability
Achieving a stable weight is a component of managing ALS, pursued through close collaboration with a multidisciplinary healthcare team, including a registered dietitian and a neurologist. These professionals can help create a personalized nutrition plan that adapts to the individual’s changing needs as the disease progresses.
For individuals receiving nutrition via a PEG tube, a dietitian plays a role in calibrating the feeding formula. This involves adjusting the type of formula, its volume, and the frequency of feedings to match the person’s specific energy requirements. The quality of nutrients is as important as the quantity of calories, with an emphasis on a balanced intake of carbohydrates, proteins, and fats.
Physical and occupational therapists also contribute to this effort indirectly. By helping to manage mobility, posture, and function for as long as possible, they support overall well-being and can have a small impact on daily energy expenditure. Any changes to diet or feeding regimens should be made only under professional guidance.