Why you need to eat less as you age

It’s harder to stay lean as you get older, but gradually reducing portion sizes each decade can help to ward off the middle-age spread.

An expanding waistline is often considered an unavoidable side effect of getting older, along with wrinkles, grey hair and poor eyesight. Lean muscle mass declines as we age, which means the body’s metabolism slows and less energy is required to keep it functioning at a baseline level. The result? The excess energy is converted to fat.

It’s unsurprising that people who continue to eat in their 40s and 50s as they did in their 20s and 30s encourage more energy to be stored as fat, because the body no longer has enough fat-burning muscle reserves to keep up with the same amount of food it once could. However, consuming fewer calories every decade means there’s a good chance of avoiding excess weight gain around the waist – and reducing the associated risk of chronic disease in the process.

Energy in, energy out
“There’s a number of reasons why our energy expenditure tends to drop as we age – and as a result, the number of calories we’re required to take in needs to come down,” professor Timothy Gill from the Boden Institute of Obesity, Nutrition, Exercise & Eating Disorders, says.

Some studies suggest that we lose about 3kg of lean muscle every decade from middle age, but there’s also evidence to suggest that much of this change is related to a sedentary lifestyle rather than age.

“Our activity drops away as we get older, particularly our vigorous activity and our resistance training, so our muscle mass tends to drop,” Gill says. “Plus, food is all around you and you tend to be wealthier as you get older. Your mind is occupied with work or family responsibilities so you become more stressed and eat in relation to your mood.”

Age-related hormonal changes, especially post-menopause, increase the likelihood that this weight will be stored around the abdomen, which is especially concerning because excess fat in this area is linked with an increased risk of heart disease, type 2 diabetes and some forms of cancer.

“In middle life, particularly for women, there’s a redistribution of fat that goes towards the middle, but for men that’s usually where it is to start with – and it’s generally hormonal and can’t be stopped completely,” associate professor Tim Crowe, from the School of Exercise and Nutrition Sciences at Deakin University, says.

Portion perfection
The good news is that getting older doesn’t have to mean getting fatter – it just means working harder to keep the weight off. Along with regular resistance training sessions, consuming fewer calories each decade will help to compensate for reduced muscle mass.

However, the body still needs the same amount of nutrients. “As your energy expenditure declines, you need to be particularly sensitive about the types of foods you eat,” Gill says. “As you get older those discretionary food items really need to be tightened because your nutrient requirements don’t decrease as you get older and you have to get those nutrients in less food.”

Dietitian Kara Landau recommends consuming more foods that are higher in protein and dietary fibre. “These two nutrients are known for keeping us satisfied for longer, so by selecting foods that are rich in protein and fibre, you’ll feel more satisfied with a smaller portion of food. The goal is to make sure you’re eating foods that are as nutrient-dense as possible.

“It’s also really important to have protein at breakfast, lunch and dinner. For example, eggs or Greek yoghurt at breakfast and fish at lunch. Some people don’t eat protein at breakfast, but it’s really important for keeping you satisfied so you don’t end up overeating refined grains as the day goes on.”

Readjusting the balance
So how much less do you really need to eat to avoid becoming overweight? “It’s very difficult to give a specific guide around the size of the calorie reduction with age, as this varies greatly among individuals and is influenced by their level of physical activity, muscularity, genetics and gender,” Gill says.

Generally, Gill says women expend 75-150 fewer calories per day each decade from their 30s until age 70, leading to about a 20 per cent decline in muscle mass.

For men, the effect is similar: they generally expend 100-200 fewer calories per day each decade between their 30s and age 70, with a 25 per cent decline of muscle mass. Hence it’s important to reduce calorie intake each passing decade.

How many daily calories do you need
These figures are approximates based on a woman of 160cm and a man of 180cm with a sedentary job and low to medium activity level. Actual energy needs for individuals will vary depending on activity, body composition, state of health, age, weight and height. Amounts increase by 300-500 calories per day for pregnant and breastfeeding women.