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Do cats lose or gain weight in heat? (Or When the Weather is Hotter)

Part of being a loving pet parent is ensuring they are getting proper nutrition and maintaining a healthy weight. Your cat’s weight will naturally fluctuate slightly, but if there’s a large loss or gain it could point to a health issue. 

Do cats lose or gain weight in heat?

The heat cycle can have quite an effect on cats. They have many behavioral changes in addition to the physical changes of the heat cycle. These can cause your cat to lose weight.

Heat Cycle In Cats

First, let’s learn about your cat’s heat cycle. Once a cat reaches sexual maturity, between 6 and 12 months old, they will begin to have heat cycles. 

Cats will have multiple heat cycles each year. This is known as polyestrus. A heat cycle will last about 2 weeks. The cycle will also repeat every 2 to 3 weeks. 

Cats will only have a heat cycle in certain seasonal conditions. Longer daylight and warmer temperatures will cause the heat cycles to begin. Cats in the Northern Hemisphere usually have cycles from February to October. Indoor cats can have cycles throughout the year, due to artificial light and climate-controlled temperatures. 

Cats are induced ovulators. This means that they do not release eggs immediately during their heat cycle. Instead, they must mate to induce the eggs to release. Once the eggs are released, they are able to get pregnant. 

If the cat doesn’t mate, she will have another heat cycle soon. If she does, she will either be pregnant, or the next cycle will take a bit longer to appear. 

Signs of Heat

A cat in heat can be a handful for their owner. They will meow frequently, sometimes letting out long wails that make you wonder if they are in pain. 

They will want to be outside, and some cats will go to great lengths to try to get outdoors. It’s their instinct to find mates. Unless there are males in the house, they must go outside to do so. 

They will be restless and potentially anxious due to their hormones. They will also groom themselves more often, particularly their private parts. 

Spraying is also common when a cat is in heat. Females will pee around the house to alert any males to their sexual status. 

A cat is also typically more affectionate when they are in heat. Your cat, who is typically pretty aloof, is suddenly rubbing all over you and hopping in your lap. 

In addition to showing affection, they will rub against you to leave their scent behind. They have scent glands on each side of their face. So, when they nuzzle you, they are also leaving behind their calling card. 

Appetite Loss

When in heat, your cat may lose their appetite. This is partly  because of the hormonal changes that occur during heat. They can leave your cat restless and not in the mood for food. 

The other reason is because they are so focused on mating that other needs take a back seat. You’ve probably had this same experience when you fell in love. 

Suddenly nothing mattered as much as being with the person. You would miss sleep and meals because you were too excited to eat, or because you simply didn’t think to do these things. Your mind was too preoccupied with your love. Cats experience these same types of feelings, only it’s lust, not love, that drives them. 

Why is my cat in heat gaining weight?

If a cat’s weight changes during heat, it’s usually because they are losing weight. If your cat is gaining weight while in heat, you may find this confusing. 

False Pregnancy

The most common reason a cat gains weight during heat is false pregnancy. When your cat comes into heat, they must have sex to ovulate. 

It usually takes 2-3 mating sessions within a 24 hour period for your cat to ovulate. Once they’ve ovulated, they can get pregnant. They will need to mate after ovulating to conceive. If they don’t, they will not get pregnant. It’s possible for your cat to ovulate and have sex without conceiving as well, just as it is possible for humans to do so. 

When your cat ovulates but doesn’t conceive, it can lead to a false pregnancy. Essentially, the body mistakenly believes it’s pregnant, so it goes through the changes of pregnancy. 

The symptoms of a false pregnancy usually occur 6-12 weeks after the heat cycle, and can continue for several months. 

Symptoms of false pregnancy include weight gain, pinking nipples, and behavioral changes including nesting and being extra affectionate. 


It’s probably the last answer you expected to see, but it is a possible cause of weight gain during heat. There are two possibilities. 

The first is that the cat is actually experiencing a heat cycle while pregnant. This is rare, but it does happen. 

The second possibility is that your cat isn’t experiencing a heat cycle. The symptoms of pregnancy and heat can be similar, so it can be easy to mistake the two. 

It’s rare to actually see a cat bleeding when they are in heat, because they are fastidious about keeping themselves clean. This makes it hard to tell the difference between heat and pregnancy. 

Too Much Food

Nearly 60% of cats in America are overweight or obese. This is a startling number with lasting health consequences. The main reason for this is overfeeding. 

Most cats are not able to regulate their food intake. If offered more than they need, they will eat it. Many owners free feed, expecting their cat to take in the calories that they need, not realizing that the cat is overeating. 

Lack of Exercise

Typically, a cat in heat will be restless and get more exercise. However, it’s possible for your cat to be less active during heat. Weight gain could also be caused by lack of activity in general, and not just during the heat period. 

Medical Reasons for Weight Gain

Hypothroidism is a common medical condition that can cause cats to gain weight. It also causes them to be lethargic and have a dull coat. The thyroid controls metabolism. When it is underactive, as with hypothyroidism, it slows the metabolism. Your cat can’t properly use the calories they consume. 

Cushing’s Disease can also cause weight gain. It causes the body to produce excess cortisol. Cortisol is a stress hormone that causes the body to store fat. It can occur due to a tumor or prolonged use of corticosteroids. 

Helping Your Cat Lose Weight

An overweight or obese cat needs to lose weight for their health. However, losing weight too quickly is dangerous as well. When calories are severely reduced, your cat’s body burns its fat stores. The liver isn’t able to tolerate high levels of fat, which can cause hepatic lipidosis. This is a potentially fatal condition that can result in liver failure. 

To help your cat loose weight safely, you’ll need to reduce their food by 20%. You can also switch them to a diet cat food. It’s also important to remove high-calorie snacks from their diet.

Healthy snacks, like carrots and fruit, can also help your cat lose weight.  Beef or turkey jerky can also be a good addition, in moderation. 

Why is my cat in heat losing weight?

It’s fairly common for a cat in heat to lose a slight amount of weight. However, the weight loss should not be drastic. 


Stress can cause your cat to lose their appetite. You’ve probably experienced this as well. You are stressed. Your stomach feels tight, and food is the last thing on your mind. The heat cycle can be stressful for your cat, so it’s not a surprise it can affect their appetite. 

Focus on Mating

When your cat is in heat, it’s hard for them to focus on anything else, including eating. If they are ignoring their food bowl during heat, it could simply be because food is the last thing on their mind. 

Problems With Food or Bowl

Your cat may be more picky about her food during heat. Some cats will refuse to eat if the food is too close to their water or litterbox. If the food bowl is dirty, this can also put them off. 

High traffic areas are another issue. Your cat wants to eat in a quiet and calm area. Eating with people moving around can be stressful. If you have multiple cats, they should be fed in separate areas. Cats prefer privacy during mealtime. 

Of course, the food itself could be the problem. If you’ve recently changed foods, your cat may not like the new flavor. If you’ve been feeding the same food for awhile, they may be bored with their food. Just like humans, cats like variety. 

Medical Reasons for Weight Loss

If your cat has lost a significant amount of weight in a short time, there may be a medical reason behind it. These reasons aren’t directly related to their heat cycle. 

Cancer is one of the most concerning and common reasons for weight loss. Other symptoms include lethargy, lack of appetite, and hiding. 

Diabetes is another potential cause. In humans, diabetes is more likely to cause weight gain. In cats, it often causes weight loss. Other symptoms include excessive thirst and urination, lack of appetite, and sweet smelling breath or urine. 

Gastrointestinal Issues

Gastrointestinal problems can also cause weight loss. If your cat’s stomach is causing them pain, they are likely to avoid eating. Some disorders can also affect food digestion and absorption. 

Common gastrointestinal issues in cats are inflammatory bowel disease, food allergies, and infections. Other symptoms include diarrhea, vomiting, and reduced appetite. You may notice your cat seems in pain during or after eating, or when using the bathroom as well. 

What to Do About Weight Loss

If your cat is losing a significant amount of weight, you should get them checked out by the vet. They can rule out physical conditions that can cause weight loss. They can also treat severe anxiety or depression that interferes with your cat’s ability to eat. 

If heat is the issue, try offering a more enticing food. Food toppers can be store-bought or homemade. Homemade topper ideas include canned pumpkin, fish oil, or a can of sardines. This may be enough to stimulate your cat’s appetite. 

Can cats lose their appetite in heat?

Yes, many cats have a reduced appetite when they are in heat. If your cat isn’t eating at all, you’ll need to visit the vet. There may be a medical reason for the change in appetite. 

If your cat is simply less interested in food or has a reduced appetite, this is probably because of their heat cycle. 

Keep track of how much they are eating. When the heat cycle stops, their appetite should return. If it doesn’t, there may be another issue affecting them. 

Do cats lose or gain weight when the weather is hotter?

Cats typically lose weight in the summer time, but this isn’t a hard and fast rule. Your cat’s weight is the result of an equation. Food and calories in is one half of the equation. The other half is how many calories they are expending each day. 

If they are consuming more calories than they are burning, they will gain weight. If they consume fewer calories than they are expending, they will lose weight. 

Loss of Appetite During Summer

Many cats lose their appetite during summer. The hotter temperatures will likely cause your cat to drink more water and eat less food. This will cause them to lose weight. 

Shorter Coat

Cats will naturally have a shorter coat in the summertime. Their coat is designed to keep them warm in the winter months. They will shed their summer coat in the fall, and grow in a thicker, warmer coat. 

In the spring, they begin to shed their winter coat in preparation for summer. This coat is lighter. It will weigh a bit less than the winter coat. It can also look like your cat is significantly thinner, because their hair is shorter. 


Your cat can pick up intestinal parasites at any time of the year, but its more common in the summer months. These parasites will make their home in your cat’s digestive tract. They feed on the blood and nutrients your cat has. This takes nutrition away from them. If they have a severe infestation, it can cause weight loss. 

Other signs of parasites include lethargy, a dull coat, diarrhea, and vomiting.