One of those internet memes that is always cropping up on online forums is "Breastmilk contains more calories than any other food." Like all internet memes, it comes in various forms--"Breastmilk contains more calories than almost any other food," "Breastmilk contains more calories and nutrients than any other food," "Breastmilk contains more calories than any other food except avocado""Breastmilk contains as many calories as melted icecream" and so on. It's usually something you hear when some mother is debating whether to start her baby on solids (because her baby seems hungry on breastmilk alone) or whether to offer more solids to her older baby or toddler who is nursing almost exclusively and is gaining poorly. Sometimes, just to add to the general drama, there is a pediatrician involved in the background who is apparently telling the mother to stop/reduce nursing because this is "filling the baby up on breastmilk" and preventing them from wanting their solids.
This is the point where someone will inevitably advising the mother to sack the pediatrician, nursenursenurse, and not bother about introducing solids/offering increased amounts of solids--or even cut back on the things or stop them completely. Given the "breastmilk contains more calories than any other food" meme, it's easy to see why. If you actually believe that breastmilk contains more calories than any other food, then logically, why would you introduce/increase solids in response to hunger or poor weight gain? In fact, if you took the idea to its logical conclusion, you should actually decrease solids or better still, take them away altogether, because surely the only thing those rotten, puny solids are going to do is fill the kid up and reduce their appetite for your calorie-festa boobie milkshakes. Clearly you should introduce solids as late as possible, or better still, never.
Since my own impression of breastmilk's flavor--oh come on, like you've never tasted your own--is that it does not taste like melted icecream, I did some research into the calories counts of solid foods commonly offered to babies using USDA figures. Very easy to do. Here's what I found:
This is a pretty reasonable "range" of vegetables, cereals, fruits and animal foods, and in terms of calorie count, breastmilk comes slap in the middle of the list; not a low-calorie food by any means, but not "melted icecream" or "richer in calories than any solid food" either, not by a long shot.
There are two conclusions one can draw from this. Firstly, look at the things in the upper part of the table with fewer calories than breastmilk: pear, carrot, squash and so on. Notice anything about them? Most of the the things which are offered to very young babies are actually pretty low in calories. So no, giving your five-month-old a few teaspoons of pureed carrot is not going to miraculously make her sleep through the night, as many disappointed parents have found out the hard way (seriously, is there anyone for whom this trick has ever actually worked?). Plus, let's face it, actually getting 100g of breastmilk into a young baby is usually easier than trying to get 100g of banana into them... as opposed to all over the floor, highchair, bib, baby's hair etc. etc.
How about rice cereal? Lest you are goggling at that last figure on the list, I should let you know that this appears to be the figure for dry baby rice; I can't seem to find a figure for rice cereal mixed with breastmilk, which is how it's usually served. Kellymom (which does things in ounces.... Americans, please get with the program and switch to metric like the rest of the planet!) gives 22kcal/ounce as the calorie count for breastmilk and 20kcal for a very watery-sounding "Baby rice cereal (2 TBS dry cereal prepared in one oz water)," so I'm going to go right ahead and assume that 100g of regular-thickness breastmilk-mixed-with-rice-cereal probably contains somewhat more calories than 100g of breastmilk, though certainly not anywhere near as much as 391kcal. That said, The Sleep Lady is something of a goddess in my household, so when she says that of the countless parents she's worked with over the years who have dutifully given their babies rice cereal every night, she has never seen any cases where actual sleep improvements have resulted, I tend to believe her. Let's face it, there are a lot of reasons why young babies wake at night.
However. The second point one might take home from the chart is that it would appear to call into question the idea that introducing or increasing solids is unnecessary or harmful for on older baby/toddler who is eating very little food and is hungry or gaining poorly.
Three other points:
(1) Breastfeeding at the breast is quite hard work for the nursling, who has to suck hard for every mouthful, and the milk comes slowly. This of course is generally a good thing as it acts as a natural corrective to overfeeding, which is probably why excessive weight gain is less common with breastfed babies. On the other hand, if a mother has a hungry or failing-to-grow child and needs to "feed them up," I suspect that this feature of breastfeeding may become a hindrance, and easy-to-eat solid foods are probably more suited to her purpose.
(2) With breastmilk a mother limited to whatever her body can produce, and at times when it is available--i.e., she's probably going to have to feed throughout the night if she is to stand a chance of providing enough calories. With solids--assuming one is not living in the South Sudan famine belt or something--one can always just go to the fridge and get more.
Granted, some women no doubt can provide more than enough calories to sustain a baby up to a year or even beyond with little or no solid food, assuming they have a strong supply and are prepared to do plenty of night feedings. According to this USDA source, a 1-month-old baby boy requires about 472 calories a day, which means a mother of twin boys would need to produce 944 calories a day in breastmilk in order to exclusively breastfeed them. A single 12-month-old baby boy, on the other hand, requires just 844 calories a day (and bear in mind that breastmilk typically becomes more calorie-dense as your child grows older). Since there most certainly are mothers who manage to exclusively breastfeed twins to a month or well beyond, it would appear that some women, at least, are capable of producing more than enough calories to feed a child healthily to a year or so. There are other reasons why babies need solids by about six months or so (iron and zinc), but calorie-wise, a baby who takes to solids slowly is probably not a problem if they are gaining well and meeting milestones. But not everyone has a terrific supply. If a child is not growing well, they probably need more food.
(3) With the exception of infants in the Gerber puree stage, it's not like we human beings actually tend to sit down and eat Plain Boiled Carrot/Spinach With Nothing Else very often. You're more likely to eat, say, steamed veggies dressed with oil or butter, which boosts the calorie count quite a bit even for those low-cal foods at the top of the list. (And you'll notice that the super calorie-rich things like avocado and olive oil weren't even included on my chart.)
One thing which seem very hard to verify is whether overconsumption of breastmilk really can "fill a child up" and stop them eating enough solid foods. My own hunch would be that if you've a child who just plays with solids, restricting nursing for a bit might be worth a try, to see if it can kickstart a child's developing a bit more of an appetite for solids... some kids are just very reluctant to try anything new and may need an initial kick up the butt to get them going. If that doesn't work, an assessment for texture/aversion issues might be an idea. I very much doubt whether stopping nursing altogether is necessary; some pediatricians are genuinely biased against extended nursing and tend to see it automatically as being the cause of any problem that a child's parents complain of.
Breastmilk appears to have plenty of calories--more than a few teaspoons of pear puree or whatever, anyway. That said, it's not true that it has more calories than any other food. If you have an mostly-breastfed older baby who's not growing too well, they probably need more solids. I think it's worth banging on about this a bit because while there is no real evidence that solids-introduction methods have any long-term effects on children, and the differences between breastmilk and formula are probably a lot smaller than many people believe, there is a ton of robust evidence suggesting that chronic shortages of calories (and iron) in the first couple of years can have long-term negative effects, especially on cognitive development.
It might seem like a no-brainer that a child not getting enough calories is bad for them, but it seems a few people really do need telling--and that people who have drunk deep of certain kinds of woo can start looking at their children through a kind of distorted lens. On Trolls With Wooden Spoons (an interesting forum created by former Mothering.com posters who had become disillusioned with the site), I remember an occasionally disturbing thread titled something along the lines of "What was the stupidest thing you ever did under the influence of Mothering.com?" (quoting from memory). One poster wrote something particularly sad. It was, roughly, "The stupidest thing I ever did because of MDC was exclusively breastfeeding my toddler, and telling myself again and again that he was a perfectly healthy toddler who just happened to be really tiny for his age." Yikes. As they say, "Rule No. 1: Feed the baby"!