New research indicates that it is actually the babies not the mothers who should be complaining of exhaustion.
A new study has shown that toddlers' daily antics can use up the equivalent adult energy of 83 rounds in a boxing ring.
Experts at Growing Up Milk have found that the average toddler expends the same energy as if an adult did 249 minutes in the boxing ring, ran 30 miles, or cycled 82 miles at 12-14mph.
The survey, called First Steps Research, highlights how a toddler's daily antics - including running around, playing in a sandpit, climbing stairs and playing in a play park - are the same as adults climbing 2,980 metres - twice the height of Ben Nevis, the UK's highest mountain, which stands at 1,344m.
This can also equate to 300 hours of competitive football - that's more than three full football matches in a row or a rowing session of six hours, the Daily Mail reported.
"If a little one saw their mum or dad run a marathon every day they would be pretty impressed. Of course, parents experience the same positive emotions when they witness the many milestones their toddler achieves each week...they are just unaware how much extra nutrition is needed to fuel this amazing development between the ages of one and three years," said Dietitian Dr Carrie Ruxton.
The study found toddlers need three times as much energy as adults and four times the amount of iron and vitamin C
In order to illustrate the difference between a toddlers' and an adult's diet, the First Steps Research worked out the average calories required to support a toddler on a daily basis by taking into consideration their weight, resting metabolic rate and energy necessary for growth, development and activity.
Each of these factors, when compared with an average 70kg adult, equated to a 3,600 calorie daily diet for an adult - enough to run marathons, climb Ben Nevis twice and box more than seven fights consecutively.
The survey found that 78 per cent of parents think that if a child eats the same meals as them in smaller portions their dietary meets are met, but in fact, toddlers require far more.
According to the study, they need three times as much energy as adults, four times the amount of iron and vitamin C, three times the amount of calcium, zinc and vitamin A, far more fats and less salt.